Add S2R functionality for HDMI and Mixer

Add S2R functionality for HDMI and Mixer

This patch adds clock gating support for HDMI and
Mixer via runtime PM routines.

	BUG=chrome-os-partner:12958
	Test=On Snow,
	DISPLAY=":0" xset dpms force off/on
	HDMI hotplug in and out
	rtcwake -m mem -s <X>
	This system behaves as expected.

Change-Id: I19e1acedc7d732a9f3c6a35918bd67c2d867144a
Signed-off-by: Shirish S <s.shirish@samsung.com>
Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/32216
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Tested-by: Shirish S <shirish@chromium.org>
Reviewed-by: Shirish S <shirish@chromium.org>
Commit-Ready: Shirish S <shirish@chromium.org>