bes2600: enable CONFIG_BES2600_TESTMODE by default + fix bit-rotted testmode plumbing

The driver implements a mac80211 testmode_cmd operation that dispatches
to a set of vendor commands (GET_TX_POWER_LEVEL, GET_TX_POWER_RANGE,
SET_SNAP_FRAME, TSM_STATS, GET_ROAM_DELAY, GET_STREAM, etc) plus the
BES2600 RF-test path (bes2600_vendor_rf_cmd → firmware
patch_wifi_testMode). The testmode handlers and the .testmode_cmd
binding in struct ieee80211_ops are conditionally compiled under
CONFIG_BES2600_TESTMODE, which previously defaulted to n.

Flip the Makefile default from n to y so wifi_testmode_cmd.o is
included in the build and the .testmode_cmd op is populated. On the
PineTab2 target kernel (linux-pinetab2 6.19.10-danctnix1, built with
CONFIG_NL80211_TESTMODE=y) this exposes the BES2600 RF-test surface
through the standard nl80211 testmode interface ('iw phy0 ...').

This also makes visible two classes of bit-rot that had accumulated
while nobody was building with CONFIG_BES2600_TESTMODE=y:

1. sta.c contains ~41 calls to bes2600_info() / bes2600_err() /
   bes2600_warn() / bes2600_dbg() / bes2600_err_with_cond() - a
   legacy log-macro family carrying a BES2600_DBG_* subsystem-id
   first argument. Neither the macros nor any of the BES2600_DBG_*
   constants are defined anywhere in the tree. The same call pattern
   appears under #if defined(BES2600_DETECTION_LOGIC) in hwio.c and
   under CONFIG_BES2600_ITP in itp.c, both normally disabled.

   Add minimal shim macros to bes_log.h that rewire the calls onto
   the existing bes_info() / bes_err() / bes_warn() / bes_devel()
   family (ignoring the subsystem id). Define BES2600_DBG_SBUS,
   BES2600_DBG_DOWNLOAD, BES2600_DBG_ITP and BES2600_DBG_TEST_MODE
   as 0 constants for documentation / grep.

2. bes2600_start_stop_tsm(), bes2600_get_tsm_params(), and
   bes2600_get_roam_delay() are declared in sta.c with external
   linkage but have no prototype in any header. All callers live in
   sta.c (inside bes2600_testmode_cmd). With CONFIG_BES2600_TESTMODE
   off the compiler never sees them; with it on gcc
   -Werror=missing-prototypes breaks the build.

   Mark the three functions static. (Keeping them file-local also
   matches their actual usage.)

Both changes are strictly scoped to make CONFIG_BES2600_TESTMODE=y
buildable; no behavioural change when the flag is off.

Tested-on: PineTab2 (BES2600WM + RK3566) running linux-pinetab2
6.19.10-danctnix1-1 with CONFIG_NL80211_TESTMODE=y. Module builds
cleanly, nl80211 testmode interface reachable via 'iw phy0 ...' from
userspace.

Signed-off-by: Markus Fritsche <fritsche.markus@gmail.com>

bes2600/sta.c

@@ -3654,7 +3654,7 @@ static int bes2600_set_power_save(struct ieee80211_hw *hw,
  *
  * Returns: 0 on success or non zero value on failure
  */
-int bes2600_start_stop_tsm(struct ieee80211_hw *hw, void *data)
+static int bes2600_start_stop_tsm(struct ieee80211_hw *hw, void *data)
 {
 	struct bes_msg_start_stop_tsm *start_stop_tsm =
 		(struct bes_msg_start_stop_tsm *) data;
@@ -3684,7 +3684,7 @@ int bes2600_start_stop_tsm(struct ieee80211_hw *hw, void *data)
  *
  * Returns: TSM parameters collected
  */
-int bes2600_get_tsm_params(struct ieee80211_hw *hw)
+static int bes2600_get_tsm_params(struct ieee80211_hw *hw)
 {
 	struct bes2600_common *hw_priv = hw->priv;
 	struct bes_tsm_stats tsm_stats;
@@ -3724,7 +3724,7 @@ int bes2600_get_tsm_params(struct ieee80211_hw *hw)
  *
  * Returns: Returns the last measured roam delay
  */
-int bes2600_get_roam_delay(struct ieee80211_hw *hw)
+static int bes2600_get_roam_delay(struct ieee80211_hw *hw)
 {
 	struct bes2600_common *hw_priv = hw->priv;
 	u16 roam_delay = hw_priv->tsm_info.roam_delay / 1000;