mac80211: fix build for 6.12.64 bump

Disable the backport shim on 6.12.64 and newer where the function
is provided by the kernel.

References:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/include/linux/hrtimer.h?h=v6.12.64&id=12493e7e888d266453d1c3898dc160178749afb3
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/include/linux/hrtimer.h?h=v6.12.64&id=d579cc549298a02ba90b7a6d20a2ba8e160f3f31

Co-Authored-by: Pascal Ernster <[email protected]>
Signed-off-by: John Audia <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/21431
Signed-off-by: Hauke Mehrtens <[email protected]>

package/kernel/mac80211/patches/build/999-kernel-6.12.64.patch

@@ -0,0 +1,19 @@
+diff --git a/backport-include/linux/hrtimer.h b/backport-include/linux/hrtimer.h
+index 3c351922c81d..d865dbf42e9b 100644
+--- a/backport-include/linux/hrtimer.h
++++ b/backport-include/linux/hrtimer.h
+@@ -17,12 +17,14 @@ static inline enum hrtimer_restart hrtimer_dummy_timeout(struct hrtimer *unused)
+ 	return HRTIMER_NORESTART;
+ }
+ 
++#if LINUX_VERSION_IS_LESS(6,12,64)
+ static inline void
+ hrtimer_update_function(struct hrtimer *timer,
+ 			enum hrtimer_restart (*function)(struct hrtimer *))
+ {
+ 	timer->function = function;
+ }
++#endif /* < 6.12.64 */
+ 
+ static inline void
+ hrtimer_setup(struct hrtimer *timer, enum hrtimer_restart (*function)(struct hrtimer *),