msm_fb: Make buffers aligned to 4K page boundary

This change makes the frame buffers aligned to the page
boundary. Improves GPU performance since accessing the
frame buffer from page boundary is faster.

CRs-fixed: 325134
Change-Id: I6ce4477f62536a3cd81064e26dc08f2b199e181b
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>