msm : mdss: fix unaligned access problem

debug offset comes from the user and can hold any value which can
cause unaligned access. This change fixes the unaligned access
problem on debug offset by properly aligning it.

Change-Id: Ic61c2651986ea6c98cc7d58e27af3e5fe6e42a88
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>