ALSA: ice1724 - constrain runtime rates for locked internal rate

The driver already defines control "Multi Track Rate Locking" which
locks the card at current rate if switched to internal clock. This patch
limits the runtime rates to this rate only, allowing proper reporting
of the card capabilities, and e.g. automatic rate conversion by the plug
plugin to the currently locked rate.

Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>