AVR32: Move addrspace.h to arch-directory, and move some functions from io.h to addrspace.h

The AVR32A architecture (which AT32UC3A-series is based on) has a
different memory layout than the AVR32B-architecture. This patch moves
addrspace.h to an arch-dependent directory in preparation for
AT32UC3A-support. It also moves some address-space manipulation
functions from io.h to addrspace.h.

Signed-off-by: Gunnar Rangoy <gunnar@rangoy.com>
Signed-off-by: Paul Driveklepp <pauldriveklepp@gmail.com>
Signed-off-by: Olav Morken <olavmrk@gmail.com>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>