msm_fb: Clean up of frame buffer 4KB alignment changes

Remove redundant code from the 4 KB alignment patch
and reduce the overhead of calculation of the hole
size by using bitwise operators in its calculation.

CRs-fixed: 325134
Change-Id: Ie2e3ea7cbb2a815ae4f50cb97e6c5be1bd72fe27
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>