msm: mdss: fix 32 bit compilation issues

Fix compilation issues with unsigned division. Also build
errors are seen for 32bit compilation as local variable of
mdp_overlay in function mdss_mdp_overlay_get_fb_pipe has
huge size which crossing the 1024 limit. Use heap instead
of stack in this case to fix the issue.

Change-Id: I67e8498421d2e116e77076637716708cfc289c96
Signed-off-by: Vishnuvardhan Prodduturi <vproddut@codeaurora.org>