MAINTAINERS: Add entry for HPE Superdome Flex (UV) maintainers

Add an entry and email addresses for people at HPE who are supporting
Linux on the Superdome Flex (a.k.a) UV platform.

 [ bp: Capitalize "linux" too :) ]

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200824221439.GA52810@swahl-home.5wahls.com