msm: mdss: enable GDSC before enabling clocks in MDP3 probe

After disabling splash in lk device was crashing during bootup because
GDSC was not turned on before eanbling the clock to read MDP version.

Fix the issue by adding calls for turning on GDSC before requesting MDP
clocks during MPD3 driver probe.

Change-Id: I6a7bc4be6a840b6ac4f0bc9201bc1a5263736df0
Signed-off-by: Sachin Bhayare <sachin.bhayare@codeaurora.org>