arm: mx6_c1: Add HDMI detection

Only enable HDMI if a connection is detected.
arm: mx6_c1: Fix Copyright of new code

This code is based on previous work done by both Boundary and
SolidRun.  Include both of them and myself as Copyright holders.
arm: mx6_c1: Restore Gate Registers from 2009 U-Boot

This brings back the default Clock Gating that was released
by SolidRun in their initial U-Boot release.  I had adopted
more generic settings when I was running into some stability
problems while testing new code.  Now that things seem stable
I am re-instituting these settings for broader testing.