msm: mdss: provide buffer height when getting plane size

When calculating the plane sizes the buffer height is what should
be passed into mdss_mdp_get_plane_sizes.

Change-Id: I3e4bab0fbfed1e2f34dbe757768a72c9a7916919
Signed-off-by: Terence Hampson <thampson@codeaurora.org>