ALSA: hda/ca0132 - Remove input select enum for ZxR

This patch removes the input select control for the ZxR, as it only has
one input option, rear microphone.

Signed-off-by: Connor McAdams <conmanx360@gmail.com>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>