staging/xgifb: Fix return of uninitialized variable

Clang warning:
drivers/staging/xgifb/XGI_main_26.c: warning: variable 'ret' is
used uninitialized whenever 'if' condition:
	if (xgifb_info->mode_idx < 0) {
evaluates to true.

drivers/staging/xgifb/XGI_main_26.c:
note: uninitialized use occurs here
	return ret;

This patch initializes the variable in this case.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/xgifb/XGI_main_26.c b/drivers/staging/xgifb/XGI_main_26.c
index fa351f9..106abc8 100644
--- a/drivers/staging/xgifb/XGI_main_26.c
+++ b/drivers/staging/xgifb/XGI_main_26.c
@@ -1921,6 +1921,7 @@
 
 	if (xgifb_info->mode_idx < 0) {
 		dev_err(&pdev->dev, "No supported video mode found\n");
+		ret = -EINVAL;
 		goto error_1;
 	}