ALSA: seq: oss: Fix running status after receiving sysex

This is a similar bug like the previous case for virmidi: the invalid
running status is kept after receiving a sysex message.

Again the fix is to clear the running status after handling the sysex.

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/3b4a4e0f232b7afbaf0a843f63d0e538e3029bfd.camel@domdv.de
Link: https://lore.kernel.org/r/20200316090506.23966-3-tiwai@suse.de


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