drm/msm/sde: avoid large memory chunk allocation on stack

Few sde functions have high stack frame size which leads to
compilation failure. The changes made move the local variable
allocation on stack to kernel heap.

Change-Id: I0ab5e856be7abc79f84467c5f261ea65957cc072
Signed-off-by: Raviteja Tamatam <travitej@codeaurora.org>