startup and genericize it so it can be reused to map other tables as well:
- Add a routine to walk a list of ACPI subtables such as those used in the
APIC and SRAT tables in the MI acpi(4) driver.
- Move the routines for mapping and unmapping an ACPI table as well as
mapping the RSDT or XSDT and searching for a table with a given signature
out into acpica_machdep.c for both amd64 and i386.
individual asm versions. The global lock is shared between the BIOS and
OS and thus cannot use our mutexes. It is defined in section 5.2.9.1 of
the ACPI specification.
Reviewed by: marcel, bde, jhb
