wifi: ath6k: silence false positive -Wno-dangling-pointer warning on GCC 12

For some reason GCC 12 decided to complain about the common
pattern of queuing an object onto a list on the stack in ath6k:

    inlined from ‘ath6kl_htc_mbox_tx’ at drivers/net/wireless/ath/ath6kl/htc_mbox.c:1142:3:
include/linux/list.h:74:19: warning: storing the address of local variable ‘queue’ in ‘*&packet_15(D)->list.prev’ [-Wdangling-pointer=]
   74 |         new->prev = prev;
      |         ~~~~~~~~~~^~~~~~

Move the warning to W=1, hopefully it goes away with a compiler
update.
Acked-by: Kalle Valo <kvalo@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/wireless/ath/ath6kl/Makefile

@@ -36,6 +36,11 @@ ath6kl_core-y += wmi.o
 ath6kl_core-y += core.o
 ath6kl_core-y += recovery.o
 
+# FIXME: temporarily silence -Wdangling-pointer on non W=1+ builds
+ifndef KBUILD_EXTRA_WARN
+CFLAGS_htc_mbox.o += -Wno-dangling-pointer
+endif
+
 ath6kl_core-$(CONFIG_NL80211_TESTMODE) += testmode.o
 ath6kl_core-$(CONFIG_ATH6KL_TRACING) += trace.o