msm: board: Guard HDMI regulator_get for errors.

Check if regulator_get returns error, if so, handle it gracefully.
If not handle properly, it will lead to crash. Regulator is required
for HDMI HPD which may differ from target to target. So a check for
perticular regulator should be taken care of.

Change-Id: I50507afec331b2a147ce512cf3b81faa92c37200
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>