ARM: Add support for 64 bit register reads/writes

Add macros to read and write to 64 bit registers.

Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>

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

Change-Id: Ied2b38e6a3803377cd271fe7b13f6cf0fc586e70