msm: mdss: Fix potential buffer overflow

arg_cfg has a size of MDSS_MAX_PANEL_LEN + 1, whereas panel_cfg has
a size of MDSS_MAX_PANEL_LEN, meaning there could be an oveflow.
Oddly enough, this was only detected by GCC and not Clang, making me
think Clang is doing some behind the scenes optimization but that
doesn't make it any less of a bug.

This was detected by CONFIG_FORTIFY_SOURCE.

Reported-by: Kristof Petho <kristof.petho@gmail.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: khusika <khusikadhamar@gmail.com>

drivers/video/msm/mdss/mdss_dsi.c

@@ -3021,7 +3021,7 @@ static struct device_node *mdss_dsi_config_panel(struct platform_device *pdev,
 	int ndx)
 {
 	struct mdss_dsi_ctrl_pdata *ctrl_pdata = platform_get_drvdata(pdev);
-	char panel_cfg[MDSS_MAX_PANEL_LEN];
+	char panel_cfg[MDSS_MAX_PANEL_LEN + 1];
 	struct device_node *dsi_pan_node = NULL;
 	int rc = 0;