msm: mdss: refactor phase step scaling

Move calculation of phase step to overlay parameters setup. This is done
to detect early whether the calculation may lead to potential overflow
in phase step. This can lead to interrupts not getting triggered for
ping pong. By detecting early and failing parameters user app can use
fallback solution.

CRs-Fixed: 486751
Change-Id: Iae402d8e97a9ef1d882ffb3e7fee92982f8b65f6
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>