msm: display: Add MDP footswitch regulator control for HDMI PLL

Add support for enabling HDMI PLL regulator along with footswitch
enable/disable to avoid PLL lock detection failures during
suspend/resume

CRs-fixed: 360135
Change-Id: I9b161cab50d2b6c39de39b588e326f5ff97cbc65
Signed-off-by: Ravishangar Kalyanam <rkalya@codeaurora.org>
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>
Signed-off-by: Ramakrishna Prasad N <crpn@codeaurora.org>

Conflicts:

	drivers/video/msm/mdp.c