alarmtimer: Change remaining ENOTSUPP to EOPNOTSUPP

BugLink: https://bugs.launchpad.net/bugs/1852110

Fix backport of commit f18ddc13 upstream.

Update backport to change ENOTSUPP to EOPNOTSUPP in
alarm_timer_{del,set}(), which were removed in
f2c45807 in v4.13-rc1.

Fixes: c22df8ea7c5831d6fdca2f6f136f0d32d7064ff9
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

kernel/time/alarmtimer.c

@@ -573,7 +573,7 @@ static void alarm_timer_get(struct k_itimer *timr,
 static int alarm_timer_del(struct k_itimer *timr)
 {
 	if (!rtcdev)
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)
 		return TIMER_RETRY;
@@ -597,7 +597,7 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 	ktime_t exp;
 
 	if (!rtcdev)
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	if (flags & ~TIMER_ABSTIME)
 		return -EINVAL;