msm: display: Add DSI clock control for MDP GDHS power collapse

Enable DSI clock and regulator before enabling/disabling power collapse
for MDP GDHS.

(cherry picked from commit ad3200279e62eff01fd1bb9136cc9c0d11e10380)

(cherry picked from commit 58c5992c710df379e26bb210e00c74da501db9d2)

Change-Id: I76b91260c61abf214e688c0dea6989ed2cfa3801
Signed-off-by: Ravishangar Kalyanam <rkalya@codeaurora.org>
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>
Signed-off-by: Ram Kumar Chakravarthy Chebathini <rcheba@codeaurora.org>

Conflicts:

	arch/arm/mach-msm/board-8064-regulator.c

Signed-off-by: Dhivya Subramanian <dthiru@codeaurora.org>