danctnix-besser: pkgrel=3 — refine Patch I, add SCS-off + GCC15 workaround

Three things bundled because they were verified together in the same
deploy cycle on ohm (kernel built fresh on boltzmann 2026-05-18):

1. 0002 (Patch I) refined: refuse only multi-channel 5 GHz scans
   (n_channels > 1).  Original Patch I refused everything, which
   blocked NM's per-frequency BSS discovery and made 5 GHz association
   impossible.  Tighter guard preserves the storm fix and unblocks
   5 GHz attachment via NM 802-11-wireless.band=a profiles.

   Verified on ohm with pkgrel=3: associated to BSSID
   c0:25:06:e6:5b:33 on 5240 MHz (ch.48), TX 150 Mbit/s MCS 7
   HT40 short-GI vs 72.2 Mbit/s on 2.4 GHz.  Pattern A still 0.

   Source-of-truth: marfrit/bes2600-dkms branch bes2600/scan-filter-5ghz
   commits 093a503 + 8cd10f4 (squashed into this single 0002 file).

2. 0003 (new): arm64 xor-neon Makefile workaround for GCC 15.2.1
   strict pragma validator vs arm_neon.h target() blocks losing
   -ffixed-x18 under SCS=y.  This is a defensive workaround;
   currently dead-coded (SCS=n below) but in place for the day SCS
   re-enable becomes possible (tracked in besser#20).

3. config: CONFIG_SHADOW_CALL_STACK=n override for the current GCC
   15.2.1 toolchain issue.  Restore to =y once GCC upstream fixes
   the arm_neon.h pragma interaction (besser#20).

pkgrel bumped 2 -> 3.

Refs: besser#1 (closed), besser#20, kernel-agent#25 (PR mirroring
this into the kernel-agent patch tree — needs follow-up to pick
up the refinement).

danctnix-besser-pkgbuild/kernel/PKGBUILD

@@ -11,7 +11,7 @@
 
 pkgbase=linux-pinetab2-danctnix-besser
 pkgver=7.0.danctnix1
-pkgrel=2
+pkgrel=3
 pkgdesc='PineTab2 (BESser bes2600 driver patchset)'
 _srcname=linux-pinetab2
 _srctag=v${pkgver%.*}-${pkgver##*.}
@@ -40,6 +40,8 @@ source=(
   ${_url_git}/releases/download/${_srctag}/${_srctag}.patch.zst{,.sig}
   0001-bes2600-besser-cumulative-series.patch
   0002-bes2600-filter-5ghz-scan.patch
+  0003-arm64-xor-neon-ffixed-x18-build-fix.patch
+  0003-arm64-xor-neon-ffixed-x18-build-fix.patch
   config  # the main kernel config file
 )
 validpgpkeys=(
@@ -52,8 +54,10 @@ b2sums=('3d9795083c8938f80f480de0d10bfd9c525640e59d5c7f22983de3f12ee42c84c31be90
         '71fe98221e802b315e54b4b10d3e8c8f376695a36bae3541d876e5776a37f3fa33c8f8dfa6e51fcbd6f5396add02e5166634165f2351836a0ea0453c172fe56c'
         'SKIP'
         'fca0a5badf762d5dbc085261cccc07ddeef96384d2ae0a426fb0412acd7a180e068cabd59f01342b7575d41889afc0f47dfbc9256801ab809f746278e6dab510'
-        '7efbd3e09f2d37aa1ed185f24775fab76b31036c7eab76f7b0a7950a24b0439c5978afcae80feb248d3e7776fa04e34ffe412a3073cc40677679f77cb18be433'
-        '19c35c69a4ed40635fb6ad108d2e0ed3d0edc682972255b4a9b719d09e377aa916e533b2e29f4aed256d3a393d77df9e11b661b690acd96edcf61eafe016f55b')
+        '396acbdcf570eada62533c0b8f505ed18077e8432249bab5b8ac8d1107cabc9489bdb91a5780446237ec4fd9ba5fc57a49dff34c16ddab60dc30513fc535f00f'
+        '2714e3c0cd8ec978ce9431418f44f578220886fcabb738c9a0c43fc3c043753960b7c47ae96e1780154d8b266a2add6098407de4ffa7aee40d77ce17e8c70df9'
+        '2714e3c0cd8ec978ce9431418f44f578220886fcabb738c9a0c43fc3c043753960b7c47ae96e1780154d8b266a2add6098407de4ffa7aee40d77ce17e8c70df9'
+        '656a998ab40cb85ee4c00f087b071a91632a6c091da2c84b0f74236b51d2dea6e9db6886625f80ad81dc249d8494ec47cd79d6dd9ea4f5e44f3cde857f861e10')
 
 export KBUILD_BUILD_HOST=archlinux
 export KBUILD_BUILD_USER=$pkgbase