msm: mdss: remove pm suspend handler

All suspend calls are handled through early suspend, using pm
suspend/resume as well can lead to HDMI being resumed before MDSS
regulator is enabled, leading to HDMI hang during resume. Remove pm
suspend handler completely since it's not needed.

CRs-Fixed: 425657
Change-Id: I0b9d072037dfdceef90d24fba50813390191f4e0
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>