Reorganize architecture-dependent header files

The architecture dependant header files in include/lib/${ARCH} and
include/common/${ARCH} have been moved to /include/arch/${ARCH}.

Change-Id: I96f30fdb80b191a51448ddf11b1d4a0624c03394
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>