msm: mdss: Enable mdp clocks before accessing panic control registers

Crashes are observed during bootup due to unclocked access of Panic
control registers. Take care of the same by enabling appropriate clocks.

Change-Id: Ic8df1f9c3c3928b9a3e9b21d63a5d9bba4f2152c
Signed-off-by: Vishnuvardhan Prodduturi <vproddut@codeaurora.org>