msm: mdss: remove pipe queue from pan display

Instead of directly queueing the data to pipe, store buffer contents in
in pipe structure during pan display. This will result in the contents
to be updated once kickoff is called, which is the expected behavior.

Change-Id: Ic6167317f32220497ca05447c896b44c33b1ee1f
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>