Optimized ARM RWSEM algorithm

RWSEM implementation for ARM using atomic functions.
Heavily based on arch/sh/include/asm/rwsem.h

Change-Id: I915a6eda5e9a3998c7748416bd2b9c108ced26e3
Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>