drm/msm/mdp5: restore cursor state when enabling crtc

Since we enabled runtime PM, we cannot count on cursor registers to
retain their values.  This can result in situations where we think the
cursor is enabled when we enable the CRTC but it is trying to scan out
null (and the rest of cursor position/size is lost), resulting in faults
and generally angering the hw when coming out of DPMS with a cursor
enabled.

stable backport note: reverting 774e39ee is also a suitable fix

Fixes: 774e39ee drm/msm/mdp5: Set up runtime PM for MDSS
Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>