msm: mdss: reset cont splash screen flag after notifying panel intf

Starting with commit a702d631, the
continuous splash screen feature flag for the secondary panel was also
disabled along with that of the primary panel. However, this should only
be done after notifying the interface drivers about the transition from
the splash screen to the boot animation. This is needed as the DSI panel
driver relies on this flag to avoid unnecessarily configuring the DSI
lanes in to the ultra low power state during this transition.

Change-Id: I59d312248c579d27913f23dc23e9c91a99549725
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>