futex: Simplify return logic

No need to assign ret in each case and break. Simply return the result
of the handler function directly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@linux.intel.com>

diff --cc kernel/futex.c
Simple merge