PM: hibernate: Add stub for pm_hibernate_is_recovering()

Randy reports that amdgpu fails to compile with the following error:
ERROR: modpost: "pm_hibernate_is_recovering" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!

This happens because pm_hibernate_is_recovering() is only compiled when
CONFIG_PM_SLEEP is set.  Add a stub for it so that drivers don't need
to depend upon CONFIG_PM.

Cc: Samuel Zhang <guoqing.zhang@amd.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Closes: https://lore.kernel.org/dri-devel/CAJZ5v0h1CX+aTu7dFy6vB-9LM6t5J4rt7Su3qVnq1xx-BFAm=Q@mail.gmail.com/T/#m2b9fe212b35fde11d58fcbc4e0727bc02ebba7b0
Fixes: c2aaddb ("PM: hibernate: add new api pm_hibernate_is_recovering()")
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20250712233715.821424-1-superm1@kernel.org
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>

Author: superm1

include/linux/suspend.h

@@ -426,8 +426,6 @@ int is_hibernate_resume_dev(dev_t dev);
 static inline int is_hibernate_resume_dev(dev_t dev) { return 0; }
 #endif
 
-bool pm_hibernate_is_recovering(void);
-
 /* Hibernation and suspend events */
 #define PM_HIBERNATION_PREPARE	0x0001 /* Going to hibernate */
 #define PM_POST_HIBERNATION	0x0002 /* Hibernation finished */
@@ -478,6 +476,7 @@ extern unsigned int lock_system_sleep(void);
 extern void unlock_system_sleep(unsigned int);
 
 extern bool pm_sleep_transition_in_progress(void);
+bool pm_hibernate_is_recovering(void);
 
 #else /* !CONFIG_PM_SLEEP */
 
@@ -508,6 +507,7 @@ static inline unsigned int lock_system_sleep(void) { return 0; }
 static inline void unlock_system_sleep(unsigned int flags) {}
 
 static inline bool pm_sleep_transition_in_progress(void) { return false; }
+static inline bool pm_hibernate_is_recovering(void) { return false; }
 
 #endif /* !CONFIG_PM_SLEEP */