mx6cuboxi: Add HDMI output support

mx6cuboxi: Add HDMI output support

Add HDMI output using PLL5 as the source for the IPU clocks,
and accurate VESA timings.

These settings are based on the patch from Soeren Moch <[email protected]>
submitted for the tbs2910 mx6 based board.

It allows the display to work properly at 1024x768@60.

This should make the hdmi output signal compatible with most if not all
modern displays.

Signed-off-by: Jon Nettleton <[email protected]>
Signed-off-by: Fabio Estevam <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Tested-by: Tom Rini <[email protected]>
Signed-off-by: Rabeeh Khoury <[email protected]>
Signed-off-by: Fabio Estevam <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Tested-by: Vagrant Cascadian <[email protected]>