arm: remove machine_desc.io_pg_offst and .phys_io

Since we're now using addruart to establish the debug mapping, we can
remove the io_pg_offst and phys_io members of struct machine_desc.

The various declarations were removed using the following script:

  grep -rl MACHINE_START arch/arm | xargs \
  sed -i '/MACHINE_START/,/MACHINE_END/ { /\.\(phys_io\|io_pg_offst\)/d }'

[ Initial patch was from Jeremy Kerr, example script from Russell King ]

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Eric Miao <eric.miao at canonical.com>