ALSA: rawmidi: remove variable dest_frames

Variable dest_frames is just being incremented and it's never used
anywhere else. The variable and the increment are redundant so
remove it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20221024130415.2155860-1-colin.i.king@gmail.com


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