drm: Add Panel Self Refresh DP addresses

Add the addresses and definitions I care about for Panel Self Refresh, as
documented in the eDP spec.

I'm sending these out before some other patches because this should be a fairly
simple one to get upstream and not require too much fuss (where the others may
have some fuss).

This file is a mess with white spacing. I tried to stay consistent with the
surrounding code.

v2: had some silly mistakes in v1 which Keith caught

Cc: Dave Airlie <airlied@redhat.com>
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Keith Packard <keithp@keithp.com>