sparc: vDSO: Silence an uninitialized variable warning

Smatch complains that "val" would be uninitialized if kstrtoul() fails.

Fixes: 9a08862a5d ("vDSO for sparc")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/vdso/vma.c

@@ -262,7 +262,9 @@ static __init int vdso_setup(char *s)
 	unsigned long val;
 
 	err = kstrtoul(s, 10, &val);
-	vdso_enabled = val;
+	if (err)
 		return err;
+	vdso_enabled = val;
+	return 0;
 }
 __setup("vdso=", vdso_setup);