iter5 sweep: remove iter1 ENTER traces (13 call sites across 4 files)

Removes the iter1 patch-0014 ENTER traces from buffer.c, image.c,
picture.c, surface.c. These were diagnostic-only entry-point logs
added during iter1's "where does Firefox RDD crash?" investigation.
With the iter1+iter2+iter3+iter4 fixes landed, the entry-point
traces are pure noise.

If a future investigation needs entry-point coverage, strace -e trace
on the libva consumer process gives equivalent visibility without
modifying the driver.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/picture.c

@@ -221,8 +221,6 @@ VAStatus RequestBeginPicture(VADriverContextP context, VAContextID context_id,
 	struct request_pool_slot *slot;
 	int slot_index;
 
-	request_log("ENTER RequestBeginPicture(ctx=%u, surf=%u)\n",
-		    context_id, surface_id);
 
 	context_object = CONTEXT(driver_data, context_id);
 	if (context_object == NULL)