drm/msm/sde: fix register access path during device boot up

During device boot up, MDP registers were directly accessed
using direct offset values. Fix this by adding new hardware
access operations for the needed hardware blocks.
For autorefresh configuration, use the existing
hardware operations.

Change-Id: I89aeac7946161fb6361654bc3ce533e3923e4842
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>