ALSA: seq: oss: remove unused inline function snd_seq_oss_timer_is_realtime

There's no callers in-tree.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200429132805.18712-1-yuehaibing@huawei.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>