ALSA: virmidi: Fix wrong error check
ALSA: virmidi: Fix wrong error check

While rewriting the code in the previous commit [316638a5030a: ALSA:
virmidi: fixed code style issues], the error check was wrongly
converted.  This resulted an Oops.

Fixes: 316638a5030a ('ALSA: virmidi: fixed code style issues')
Reported-by: Fengguang Wu <24f7fe9d205c8a9f6ade0c2894e14303ca16087f@intel.com>
Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs