fbdev: bfin_adv7393fb: new Blackfin ADV7393 driver

Driver for ADV7393 add-on card for multiple Blackfin boards.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>