msm: mdss: Enable GDSC before enabling clocks in mdp3 probe

For splash disable in LK or simulated panel / no panel connected
usecases, device was crashing at kernel bootup as GDSC was not
turned on before enabling the clock to read MDP version.

Fix this by adding calls for turning on GDSC before enabling
clocks to read MDP version.

Change-Id: I16413a33c895294acb049e78d55bc3ec89746f1e
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>