imx-drm: Add HDMI support

[Shawn Guo]

On Mon, Oct 21, 2013 at 10:34:48AM +0100, Russell King - ARM Linux wrote:
> However, the IPU is more stable with switching to bypass while it relocks
> than not.

As far as I know, FSL kernel has always been doing relock without
switching to bypass, and I haven't heard unstable IPU issue from their
testing.  Do you have a case that I can set up here to see the issue?

Shawn

> > > Here's a diff which updates the av PLL to do this:
> > 
> > Some other PLLs needs update too.  I will cook up patches to fix these
> > problems.
> 
> Yes, I only changed the set_rate on the AV codecs as I haven't tested
> that on the others.