msm_fb: display: perform data flush for each data path separately

Performing data flush on stage commit causes some frame updates to be
missed waiting for stage commit, this can lead to old data being
overwritten while it's being displayed causing visible corruption.
Change flush to happen on each frame update to avoid corruptions.

CRs-Fixed: 341597
Change-Id: If91800068d2bfd5a2e43fe3e2a96c457e173763d
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>