ALSA: drivers: opl3: fix useless self-comparison

Sparse throws the following warning:

sound/drivers/opl3/opl3_midi.c:183:60: error: self-comparison always
evaluates to false

This is likely a 16+ year old confusion between vp2 and vp.

Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210526192957.449515-1-pierre-louis.bossart@linux.intel.com


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