msm: display: sync point handling in blanking

Release all fences when go to blank

(cherry picked from commit 2575a4aa634aec1c198dd8bc851c5a002dff2278)

Change-Id: I9d6a1f4ccd97b188497866b7f27cd9d3f84c94fc
Signed-off-by: Ken Zhang <kenz@codeaurora.org>
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>