drm/msm: fix inconsequential typo

Small typo I noticed in the mdp4_plane code.. no consequence because
PIPE_SRC_XY and PIPE_DST_XY have same register layout.
Signed-off-by: NRob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/mdp/mdp4/mdp4_plane.c

@@ -170,8 +170,8 @@ int mdp4_plane_mode_set(struct drm_plane *plane,
 			MDP4_PIPE_DST_SIZE_HEIGHT(crtc_h));
 
 	mdp4_write(mdp4_kms, REG_MDP4_PIPE_DST_XY(pipe),
-			MDP4_PIPE_SRC_XY_X(crtc_x) |
-			MDP4_PIPE_SRC_XY_Y(crtc_y));
+			MDP4_PIPE_DST_XY_X(crtc_x) |
+			MDP4_PIPE_DST_XY_Y(crtc_y));
 
 	mdp4_plane_set_scanout(plane, fb);