Spelling fix
Add missing session route to printf.run
core: Be more precise in IO_MEM error message
base-hw: Avoid early calls of cmpxchg

This patch eliminates calls of 'cmpxchg' prior enabling the MMU. This is
needed because the 'ldrex' and 'strex' instructions do not always work
with MMU and L1 cache disabled, i.e., on Raspberry Pi.
base-hw: Make memory_region_attr CPU-specific

This patch moves the implementation of the 'Arm::memory_region_attr'
function from the generic ARM code to the ARM v6/v7 specific code
to enable the customization of page-table bits depending on the
specific CPU core type. I.e., the ARM1176 apparently does not cope
well with setting the 'Tex::bits(2)' for MMIO mappings.
base-hw: Enable caches on ARM v6
base-hw: Support for Raspberry Pi