MAINTAINERS: Cleanup SGI-related entries

UV platforms are the only ones which currently use the XP/XPC/XPNET
driver, so it seems fair HPE should take some responsibility as
maintainers of it; so add Mike Travis and Steve Wahl. Cliff Whickman's
email address is no longer valid, so remove it. Robin Holt was contacted
and wishes to remain as a maintainer.

Update Dimitri Sivanich's email address for the SGI GRU driver.

Add Mike Travis to HPE Superdome Flex (UV) platform.

 [ bp: Massage commit message. ]
Acked-by: Robin Holt <robinmholt@gmail.com>
Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201019203533.GA1203217@swahl-home.5wahls.com

MAINTAINERS

@@ -15833,13 +15833,14 @@ F:	include/linux/sfp.h
 K:	phylink\.h|struct\s+phylink|\.phylink|>phylink_|phylink_(autoneg|clear|connect|create|destroy|disconnect|ethtool|helper|mac|mii|of|set|start|stop|test|validate)
 
 SGI GRU DRIVER
-M:	Dimitri Sivanich <sivanich@sgi.com>
+M:	Dimitri Sivanich <dimitri.sivanich@hpe.com>
 S:	Maintained
 F:	drivers/misc/sgi-gru/
 
 SGI XP/XPC/XPNET DRIVER
-M:	Cliff Whickman <cpw@sgi.com>
 M:	Robin Holt <robinmholt@gmail.com>
+M:	Steve Wahl <steve.wahl@hpe.com>
+R:	Mike Travis <mike.travis@hpe.com>
 S:	Maintained
 F:	drivers/misc/sgi-xp/
 
@@ -19085,6 +19086,7 @@ F:	arch/x86/platform
 
 X86 PLATFORM UV HPE SUPERDOME FLEX
 M:	Steve Wahl <steve.wahl@hpe.com>
+R:	Mike Travis <mike.travis@hpe.com>
 R:	Dimitri Sivanich <dimitri.sivanich@hpe.com>
 R:	Russ Anderson <russ.anderson@hpe.com>
 S:	Supported