ALSA: hdac: Fix to read the correct offset of spcap/link register

SPCAP and Mutilink register offset were incorrect as offset needs
to be based on capability offset. So correct the offset for
read/write of spcap/link register.

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>