drm/msm/sde: continue with hw init if splash memory is not found

For continuous splash screen disabled use cases, it is possible that
no reserved memory region for the splash screen buffer is specified.
In such cases, set software sate to continuous splash disabled and
continue with the driver hardware initialization sequence.

Change-Id: I274335340111f4c77da9a06fd6b42c4e71cdea67
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>