msm: sde: delay done handler for inline rotation

Reset the completion object during inline rotation commits
so that the done handler is delayed until a 'inline start'
command has been received from the external DRM driver.

CRs-Fixed: 2046958
Change-Id: I81ab1ef5706dbb38e3d9f771f1882209e9988c7d
Signed-off-by: Clarence Ip <cip@codeaurora.org>