Staging: rtl8723bs: fix an error code in isFileReadable()

The caller only cares about zero vs non-zero so this code actually works
fine but we should be returning a negative error code instead of a valid
pointer casted to int.

Fixes: 554c0a3a ("staging: Add rtl8723bs sdio wifi driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/osdep_service.c

@@ -160,7 +160,7 @@ static int isFileReadable(char *path)
 		oldfs = get_fs(); set_fs(get_ds());
 
 		if (1!=readFile(fp, &buf, 1))
-			ret = PTR_ERR(fp);
+			ret = -EINVAL;
 
 		set_fs(oldfs);
 		filp_close(fp, NULL);