msm: mdss: Fix error roll back sequence during core on.

When core power enable fails for some reason, current code disables
hpd power in the roll back which is unnecessary. Correct this mistake.

Change-Id: Ia5ed63edb017ade44950058c9d6071e8eb5d7884
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>