ALSA: cmipci: Drop stale variable assignment

Since the recent code refactoring using devres, the variable cm in
snd_cmipci_probe() is no longer referred.

Fixes: 87e082ad ("ALSA: cmipci: Allocate resources with device-managed APIs")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/cc6383a2-cafb-ffe7-0b4f-27a310a1005c@intel.com
Link: https://lore.kernel.org/r/20211112103137.9504-1-tiwai@suse.de


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