Optimized ARM RWSEM algorithm

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

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

Change-Id: If6cf6e35942947e0e96d5c20acfe98c68cc7c6c9