drm/bridge: ti-sn65dsi86: Avoid possible buffer overflow

Smatch error:buffer overflow 'ti_sn_bridge_refclk_lut' 5 <= 5.

Fixes: cea86c5 ("drm/bridge: ti-sn65dsi86: Implement the pwm_chip")
Signed-off-by: Su Hui <suhui@nfschina.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230608012443.839372-1-suhui@nfschina.com

Author: Su Hui

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -298,6 +298,10 @@ static void ti_sn_bridge_set_refclk_freq(struct ti_sn65dsi86 *pdata)
 		if (refclk_lut[i] == refclk_rate)
 			break;
 
+	/* avoid buffer overflow and "1" is the default rate in the datasheet. */
+	if (i >= refclk_lut_size)
+		i = 1;
+
 	regmap_update_bits(pdata->regmap, SN_DPPLL_SRC_REG, REFCLK_FREQ_MASK,
 			   REFCLK_FREQ(i));