[ALSA] sound/pcmcia/vx/vxpocket.c: fix an if() condition

It seems noone ever tried to use this driver with more than one device.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>