drm/msm/dpu: fix comparing pointer to 0 in dpu_vbif.c

Fixes coccicheck warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c:27:51-52: WARNING comparing pointer to 0
drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c:109:51-52: WARNING comparing pointer to 0
drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c:167:12-13: WARNING comparing pointer to 0
drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c:167:22-23: WARNING comparing pointer to 0
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c

@@ -24,7 +24,7 @@ static int _dpu_vbif_wait_for_xin_halt(struct dpu_hw_vbif *vbif, u32 xin_id)
 	int rc;
 
 	if (!vbif || !vbif->cap || !vbif->ops.get_halt_ctrl) {
-		DPU_ERROR("invalid arguments vbif %d\n", vbif != 0);
+		DPU_ERROR("invalid arguments vbif %d\n", vbif != NULL);
 		return -EINVAL;
 	}
 
@@ -106,7 +106,7 @@ static u32 _dpu_vbif_get_ot_limit(struct dpu_hw_vbif *vbif,
 	u32 val;
 
 	if (!vbif || !vbif->cap) {
-		DPU_ERROR("invalid arguments vbif %d\n", vbif != 0);
+		DPU_ERROR("invalid arguments vbif %d\n", vbif != NULL);
 		return -EINVAL;
 	}
 
@@ -164,7 +164,7 @@ void dpu_vbif_set_ot_limit(struct dpu_kms *dpu_kms,
 
 	if (!vbif || !mdp) {
 		DPU_DEBUG("invalid arguments vbif %d mdp %d\n",
-				vbif != 0, mdp != 0);
+				vbif != NULL, mdp != NULL);
 		return;
 	}