Revert "msm_fb: display: wait4vsync after timing generator is turned off"

This reverts commit a1c739fb7cc53328e87452a288cd4c57cf0da255.
Revert "msm_fb: display: replace msleep with wait4vsync"

This reverts commit 72d0e880926836ccdd77991a7eeda66f3e7f3b92.