x86/uv: Update HPE Superdome Flex Maintainers

Mike Travis has retired. His expertise will be sorely missed.
Remove Mike's entry under SGI XP/XPC/XPNET DRIVER.
Replace Mike's entry under UV HPE SUPERDOME FLEX.

Signed-off-by: Justin Ernst <justin.ernst@hpe.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Joel Granados <j.granados@samsung.com>
Link: https://lore.kernel.org/all/20230801155756.22308-1-justin.ernst%40hpe.com

Author: justinrernst

MAINTAINERS

@@ -19283,7 +19283,6 @@ F:	drivers/misc/sgi-gru/
 SGI XP/XPC/XPNET DRIVER
 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/
 
@@ -23142,7 +23141,8 @@ 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:	Justin Ernst <justin.ernst@hpe.com>
+R:	Kyle Meyer <kyle.meyer@hpe.com>
 R:	Dimitri Sivanich <dimitri.sivanich@hpe.com>
 R:	Russ Anderson <russ.anderson@hpe.com>
 S:	Supported