sched/wait: Improve __var_waitqueue() code generation

Since we fixed hash_64() to not suck there is no need to play games to
attempt to improve the hash value on 64-bit.

Also, since we don't use the bit value for the variables, use hash_ptr()
directly.

No change in functionality.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/wait_bit.c

@@ -151,12 +151,7 @@ EXPORT_SYMBOL(wake_up_bit);
 
 wait_queue_head_t *__var_waitqueue(void *p)
 {
-	if (BITS_PER_LONG == 64) {
-		unsigned long q = (unsigned long)p;
-
-		return bit_waitqueue((void *)(q & ~1), q & 1);
-	}
-	return bit_waitqueue(p, 0);
+	return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
 }
 EXPORT_SYMBOL(__var_waitqueue);