power: supply: apm_power: only unset own apm_get_power_status

Mirroring drivers/macintosh/apm_emu.c, this means that
modprobe apm_power && modprobe $anotherdriver && modprobe -r apm_power
leaves $anotherdriver's apm_get_power_status instead of deleting it.

Fixes: 3788ec932bfd ("[BATTERY] APM emulation driver for class batteries")
Signed-off-by: Ahelenia Ziemiańska <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/apm_power.c

···
 
 static void __exit apm_battery_exit(void)
 {
-	apm_get_power_status = NULL;
+	if (apm_get_power_status == apm_battery_apm_get_power_status)
+		apm_get_power_status = NULL;
 }
 
 module_init(apm_battery_init);