disp: msm: add msm framebuffer emulation

This change copies msm_fbdev.c from msm-4.19 kernel, which adds
frame buffer support to display driver. And this file is from
msm-4.19 commit <a6869840> ("drm/msm: cleanup display drivers
to restore upstream"). It's revised to fix two failures, one is
line-over-80, the other is banned function usage.

Change-Id: Icbb0fe10282a26fa5269bd20c31fd3adec82a136
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>
Signed-off-by: Ray Zhang <rayz@codeaurora.org>