arm: mx6_c1: Fix HDMI output

Set the sync flag so the clock polarity bit is not set for the
display.  Setting this bit caused jitter and bad picture quality
when outputting to hdmi.
arm: mx6_c1: Enable console use without serial

For now this enables the console on the hdmi output and probes
for usb keyboard for input on init.  We move the display setup
to early init so there is time for the user to see what they
should do.

This is a testing configuration while we are in the development
phase. The boot procedure should probably be expanded to catch
a hotkey to break out of the splash screen instead of showing
the console by default.

FIXME: USB Keyboard input can be laggy and inconsistent
arm: mx6_c1: Expand boot script

This commit adds support for booting both ext and fat filesystems.
It also adds importing a uEnv.txt if it exists.  These are
strictly for testing right now and will change a lot of the next
month or so.