ENGR00177737-2: add HDMI sii902x support in mx6q-arm2

ENGR00177737-2: add HDMI sii902x support in mx6q-arm2

test with
video=mxcfb0:dev=sii902x_hdmi,1024x768M@60,if=RGB24 disable_mipi_dsi

Note:
1. currently we use the same ipu setting port with on chip HDMI,
if we need coexist need change the on chip HDMI ipu settings.
2. need remove MIPI DSI initial with 'disable_mipi_dsi' in kernel command line,
as mipi dsi reset will reset on board sii902x as well.
3. change the I2C2 work at 100K not 400K, to be compatible with EDID spec.
4. the side effect is that Sii902x will have to use "sii902x_hdmi",
instead of "hdmi" as before

Signed-off-by: Hake Huang <b20222@freescale.com>