ALSA: hda/realtek - Fix resume of multiple input sources

When there are multiple input sources, the driver wrongly overwrites with
the value of the last input source on other slots at resume.  Thus the
primary input source may be shown wrongly.

Reported-and-tested-by: Julian Sikorski <belegdol@gmail.com>
Cc: <stable@kernel.org> [v3.1+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>