dres0280_rev_a: RAM and serial-Post

known issues: missing mux configuration

Signed-off-by: Eik Binschek <binschek@dresearch-fe.de>
add DDR3-RAM mux settings

Signed-off-by: Eik Binschek <binschek@dresearch-fe.de>
dres0280_rev_a: renove wrong initialisation

renove wrong initialisation

Signed-off-by: Eik Binschek <binschek@dresearch-fe.de>