msm: mdss: adjust mdss_mdp_get_plane_sizes parameters init order

Parameter mdss_mdp_plane_sizes must be cleared to 0 before returning
under an error condition, otherwise caller function will use the
uninitialized mdss_mdp_plane_sizes values and caused incorrect
operation.

Change-Id: I856b17ce9e917cc450040463ec34b7309d34b9b5
Signed-off-by: Benjamin Chan <bkchan@codeaurora.org>