DRAM controller magic values cleanup

This patch tries to cleanup as much of the magic values in dram.c as
possible. Obviously for some registers we have no information so cannot
fill those in. No actually code changes where made. This patch is based
on the most recent dram.c; e.g. from A20.

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Add more info based on the A20 boot0 dump

Define missing register names and add all sun7 features

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>