fex: a80: Add A80 Optimus Board

This is the fex file found in the SDK from Merrii. It may not be
entirely correct.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
fex: a80: Update Optimus Board dram parameters

The parameters were fetch from boot0 and u-boot headers on the eMMC,
compared and merged into the fex file.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>