sunxi: video: Add cfb console driver for sunxi

This adds a fixed mode hdmi driver for the sunxi platform. The fixed
mode is a relatively safe 1024x768, more complete EDID handling is
currently not provided. Only HDMI is supported today.

This code is enabled when HPD detects an attached monitor.

Current config is such that 8MB is shaved off at the top of the RAM.
This avoids several memory handling issues, most significant is the fact
that on linux on ARM you are not allowed to remap known RAM as IO. A
clued in display driver will be able to recycle this reserved RAM in
future though.

cfbconsole was chosen as it provides the most important functionality: a
working u-boot console, allowing for the debugging of certain issues
without the need for a UART.

Signed-off-by: Luc Verhaegen <libv@skynet.be>
[hdegoede@redhat.com: Major cleanups and some small bugfixes]
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Ian Campbell <ijc@hellion.org.uk>