msm: mdss: perform proper clock handoff during cont. splash screen

During continuous splash screen need to ensure clocks are properly ref
counted once and released once handoff has happened. Doing it in
different places can lead to inproper order and cause clocks to be
disabled. Fix this by centralizing this into footswitch ctrl which is
called when continous splash screen is enabled.

Change-Id: I17f3d5517d9a0583221fdb5c354bf1992ddeddbd
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>