drm/msm/sde: handle smmu handoff for continuous splash

Continuous splash requires frame to be pushed from buffer
during boot up. So initializing SMMU during probe will
affect this functionality. Hence SMMU initalization
has to be done only after disabling auto refresh. This
change handles SMMU handoff for continuous splash
usecase.

Change-Id: I1b52434c2505a0737bdd31a7196c1bbefb18d23f
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>