msm: mdss: Perform splash cleanup on slave control

During continuous splash handoff on video mode panels, the
cleanup is currently performed only on the master control. This
causes occasional memory fault in dual control configurations.
This change calls cleanup on both master and slave controls
if applicable.

Change-Id: If0bcad0686efd5f2aba0efa6992e1d348aca213f
Signed-off-by: Rajkumar Subbiah <rsubbia@codeaurora.org>