ALSA: rawmidi: Take open_mutex around parameter changes

The input/output parameter changes are pretty intrusive, possibly
involving with the buffer resizing operation.  Hence those should be
performed exclusively; otherwise some ugly race could happen.

This patch puts the existing open_mutex for snd_rawmidi_input_params()
and *_output_params() for protecting the concurrent calls.  Since
those are exported, it's also meant for hardening from the external
calls, too.

Link: https://lore.kernel.org/r/20220617144051.18985-4-tiwai@suse.de


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