drm/msm/disp/mdp5/mdp5_crtc: Make local function 'mdp5_crtc_setup_pipeline()' static

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c:581:5: warning: no previous prototype for ‘mdp5_crtc_setup_pipeline’ [-Wmissing-prototypes]

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: freedreno@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c

@@ -577,7 +577,7 @@ static void mdp5_crtc_atomic_enable(struct drm_crtc *crtc,
 	mdp5_crtc->enabled = true;
 }
 
-int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
+static int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
 				    struct drm_crtc_state *new_crtc_state,
 				    bool need_right_mixer)
 {