msm: mdss: Prevent post processing resume misconfiguration

Fix incorrect use of dspp number instead of display number for post
processing setting arrays. Fix resume method from overwriting existing
dirty flags for each display.

Change-Id: I00212a7309784a7886823f7b5ce6bcb5b94205c1
Signed-off-by: Carl Vanderlip <carlv@codeaurora.org>