ALSA: rawmidi: Make internal functions local static

__snd_rawmidi_transmit_peek() and __snd_rawmidi_transmit_ack() are
never called from the outside.  Let's make them local static and
unexport them.

Link: https://lore.kernel.org/r/20220617144051.18985-2-tiwai@suse.de


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