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 <smoch@web.de>
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 <jon.nettleton@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Rabeeh Khoury <rabeeh@solid-run.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Vagrant Cascadian <vagrant@aikidev.net>