PM: sleep: Drop spurious WARN_ON() from pm_restore_gfp_mask()

Commit 35e4a69 ("PM: sleep: Allow pm_restrict_gfp_mask()
stacking") introduced refcount-based GFP mask management that warns
when pm_restore_gfp_mask() is called with saved_gfp_count == 0.

Some hibernation paths call pm_restore_gfp_mask() defensively where
the GFP mask may or may not be restricted depending on the execution
path. For example, the uswsusp interface invokes it in
SNAPSHOT_CREATE_IMAGE, SNAPSHOT_UNFREEZE, and snapshot_release().
Before the stacking change this was a silent no-op; it now triggers
a spurious WARNING.

Remove the WARN_ON() wrapper from the !saved_gfp_count check while
retaining the check itself, so that defensive calls remain harmless
without producing false warnings.

Fixes: 35e4a69 ("PM: sleep: Allow pm_restrict_gfp_mask() stacking")
Signed-off-by: Youngjun Park <youngjun.park@lge.com>
[ rjw: Subject tweak ]
Link: https://patch.msgid.link/20260322120528.750178-1-youngjun.park@lge.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: youngjuni

kernel/power/main.c

@@ -40,7 +40,7 @@ void pm_restore_gfp_mask(void)
 {
 	WARN_ON(!mutex_is_locked(&system_transition_mutex));
 
-	if (WARN_ON(!saved_gfp_count) || --saved_gfp_count)
+	if (!saved_gfp_count || --saved_gfp_count)
 		return;
 
 	gfp_allowed_mask = saved_gfp_mask;