drm/rockchip: vop: Init vskiplines in scl_vop_cal_scale()

Currently we are calling scl_vop_cal_scale() to get vskiplines for yrgb
and cbcr. So the cbcr's vskiplines might be an unexpected value if the
second scl_vop_cal_scale() didn't update it.

Init vskiplines in scl_vop_cal_scale() to avoid that.
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20180223062250.10470-1-jeffy.chen@rock-chips.com

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -256,6 +256,9 @@ static uint16_t scl_vop_cal_scale(enum scale_mode mode, uint32_t src,
 {
 	uint16_t val = 1 << SCL_FT_DEFAULT_FIXPOINT_SHIFT;
 
+	if (vskiplines)
+		*vskiplines = 0;
+
 	if (is_horizontal) {
 		if (mode == SCALE_UP)
 			val = GET_SCL_FT_BIC(src, dst);
@@ -296,7 +299,7 @@ static void scl_vop_cal_scl_fac(struct vop *vop, const struct vop_win_data *win,
 	uint16_t vsu_mode;
 	uint16_t lb_mode;
 	uint32_t val;
-	int vskiplines = 0;
+	int vskiplines;
 
 	if (dst_w > 3840) {
 		DRM_DEV_ERROR(vop->dev, "Maximum dst width (3840) exceeded\n");