msm: mdss: add support to control dcs brightness with HS state

Some special panels may need high speed mode to send brightness
to avoid panel issues, adding this change can make a better user
experience using these panels.

Change-Id: Id2cd4b3652892cc7677d7c6863a67d93e24d980f
Signed-off-by: Yahui Wang <yahuiw@codeaurora.org>