futex: Cleanup generic SMP variant of arch_futex_atomic_op_inuser()

The generic SMP variant of arch_futex_atomic_op_inuser() returns always
-ENOSYS so the switch case and surrounding code are pointless. Remove it
and just return -ENOSYS.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lkml.kernel.org/r/12bdaca8-99eb-e576-f842-5970ab1d6a92@virtuozzo.com

include/asm-generic/futex.h

@@ -118,26 +118,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 static inline int
 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 {
-	int oldval = 0, ret;
-
-	pagefault_disable();
-
-	switch (op) {
-	case FUTEX_OP_SET:
-	case FUTEX_OP_ADD:
-	case FUTEX_OP_OR:
-	case FUTEX_OP_ANDN:
-	case FUTEX_OP_XOR:
-	default:
-		ret = -ENOSYS;
-	}
-
-	pagefault_enable();
-
-	if (!ret)
-		*oval = oldval;
-
-	return ret;
+	return -ENOSYS;
 }
 
 static inline int