armv8: layerscape: add missing RCW source defines

A board might need to get the source of the RCW word, which is also the
boot source in most cases.

These defines are taken from the LS1028A and I expect they are the same
across the SoCs with the same chassis, after all, there was already a
reset source for NOR flash.

Signed-off-by: Michael Walle <michael@walle.cc>
1 file changed