ACPI: Remove ./drivers/acpi/atomicio.[ch]

With the conversion of atomicio's routines in place (see commits
6f68c91c and 700130b4

), atomicio.[ch] can be removed, replacing
the APEI specific pre-mapping capabilities with the more generalized
versions that drivers/acpi/osl.c provides.

Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>