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>

Conflicts:
	arch/arm/include/asm/rwsem.h

	modificado: arch/arm/Kconfig
	modificado: arch/arm/include/asm/rwsem.h
Tweak the Deadline I/O Scheduler
Set this as default for optimal performance as well.