ALSA: rawmidi: Take buffer refcount while draining output

ALSA: rawmidi: Take buffer refcount while draining output

Although snd_rawmidi_drain_output() may take some long time, it has no
protection and intrusive operations like the buffer resize may happen
meanwhile.  For making the operation a bit more robust, this patch
takes the buffer refcount for blocking the buffer resize.

Also, as this function is exported, in theory, it might be called
asynchronously from the stream open/close state.  For avoiding the
missing refcount, now the close call checks the buffer refcount, too.

Link: https://lore.kernel.org/r/20220617144051.18985-6-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>