drm/imx: imx-ldb: Disable both channels for split mode in enc->disable()

Both of the two LVDS channels should be disabled for split mode
in the encoder's ->disable() callback, because they are enabled
in the encoder's ->enable() callback.

Fixes: 6556f7f8 ("drm: imx: Move imx-drm driver out of staging")
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/imx/imx-ldb.c

@@ -296,18 +296,19 @@ static void imx_ldb_encoder_disable(struct drm_encoder *encoder)
 {
 	struct imx_ldb_channel *imx_ldb_ch = enc_to_imx_ldb_ch(encoder);
 	struct imx_ldb *ldb = imx_ldb_ch->ldb;
+	int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
 	int mux, ret;
 
 	drm_panel_disable(imx_ldb_ch->panel);
 
-	if (imx_ldb_ch == &ldb->channel[0])
+	if (imx_ldb_ch == &ldb->channel[0] || dual)
 		ldb->ldb_ctrl &= ~LDB_CH0_MODE_EN_MASK;
-	else if (imx_ldb_ch == &ldb->channel[1])
+	if (imx_ldb_ch == &ldb->channel[1] || dual)
 		ldb->ldb_ctrl &= ~LDB_CH1_MODE_EN_MASK;
 
 	regmap_write(ldb->regmap, IOMUXC_GPR2, ldb->ldb_ctrl);
 
-	if (ldb->ldb_ctrl & LDB_SPLIT_MODE_EN) {
+	if (dual) {
 		clk_disable_unprepare(ldb->clk[0]);
 		clk_disable_unprepare(ldb->clk[1]);
 	}