The aspeed video IP has some differences between SoC families. Currently
the driver decides which registers to use at compile time, which means
a single kernel can not be used between platforms.

Switch to using runtime configuration of the registers that vary between
SoC families. This is in preparation for upcoming ast2600 support.

[hverkuil: replace ;; by ;]
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>