[ALSA] cmipci - Allow to disable integrated FM port

The driver didn't allow to disable the integrated FM port (if available),
and this annoyed people who don't want FM port.  Now fm_port=0 disables
the FM port unconditionally.  fm_port=1 is used for enabling the integrated
FM port (as default).
Also fixed the documentation about this option.
Fix ALSA bug#2491.

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