x86/platform/uv: Fix missing OEM_TABLE_ID

Testing shows a problem in that the OEM_TABLE_ID was missing for
hubless systems.  This is used to determine the APIC type (legacy or
extended).  Add the OEM_TABLE_ID to the early hubless processing.

Fixes: 1e61f5a9

 ("Add and decode Arch Type in UVsystab")
Signed-off-by: Mike Travis <mike.travis@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201105222741.157029-2-mike.travis@hpe.com