ARM: dts: aspeed: Enable video engine on romulus and wtherspoon

Enable the video engine and add it's optional reserved memory region.
Use 32MB for the reserved memory since the video engine could need up to
two 1920x1200@32bpp source buffers.

Source buffers: 2 * 1920 * 1200 * 4 = 18432000 bytes
In addition, the V4L2 subsystem will allocate any number of compression
buffers, each at most 1/8th the size of the source buffer.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>