ARM: imx: Add LVDS general-purpose clocks to i.MX6Q

The i.MX6 has two general-purpose LVDS clocks that can be driven
from a variety of sources.  This patch adds a mux and a gate for
both of these clocks.

Signed-off-by: Sean Cross <xobs@kosagi.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>