alarmtimer: Change remaining ENOTSUPP to EOPNOTSUPP

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: c22df8ea



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>