msm: mdss: hdmi: retain clock state after successful handoff

When HDMI is selected as the primary interface, we want to
retain the HDMI clock state after a successful handoff to ensure
that the interface continues to send data to the sink. We achieve
this by maintaining the HDMI PHY status when we detect that
handoff is in progress.

Change-Id: I0aaefc96d63b9eaf3928c11b5dab51cce99e1dc3
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>