x86/platform/uv: Add and decode Arch Type in UVsystab

When the UV BIOS starts the kernel it passes the UVsystab info struct to
the kernel which contains information elements more specific than ACPI,
and generally pertinent only to the MMRs. These are read only fields
so information is passed one way only. A new field starting with UV5 is
the UV architecture type so the ACPI OEM_ID field can be used for other
purposes going forward. The UV Arch Type selects the entirety of the
MMRs available, with their addresses and fields defined in uv_mmrs.h.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mike Travis <mike.travis@hpe.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Link: https://lkml.kernel.org/r/20201005203929.148656-7-mike.travis@hpe.com