msm: mdss: Fix DTM state entry check in pp module

DTM state should be updated if framebuffer structure
is accessible for the pipe. Wrong check fails the
DTM state update and does not provide an exclusive
access to PP blocks on SSPP.

Change-Id: I170182c2d59c5f09d1cb911f61f3e0a1af91b067
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>