msm: mdss: verify display status for continuous splash screen

The continuous splash screen feature requires support
from both lk and kernel.  This change check the case
where the lk enables the continuous splash screen, but
kernel is not enabling it in the device tree.

Change-Id: I68fc474e87aad00760f89ee4582ae60ee5577bbf
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>