drm/msm/sde: avoid reprogramming display pipeline with continuous splash

Bootloader does interface programming and basic display pipeline setup
while enabling continuous splash. Reprogramming some of those single
buffer registers may drive the hardware to a bad state. This change
avoids reprogramming those registers while handing off on first commit.

Change-Id: I9f24e0a3276998feea98322a256c216161c35eb8
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>