MAINTAINERS: Update from @linux.vnet.ibm.com to @linux.ibm.com

IBM's patch-friendly email infrastructure is changing domains from
@linux.vnet.ibm.com to @linux.ibm.com, which if nothing else might
save a bit of typing.  This commit therefore updates us stragglers'
email addresses in the MAINTAINERS file.  The old addresses are
expected to continue to work for a few more months.

While in the neighborhood, remove some obsolete entries, which results
in an orphaned subsystem: "JSM Neo PCI based serial card".

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Douglas Miller <dougmill@linux.ibm.com>
Cc: Eddie James <eajames@linux.ibm.com>
Cc: Frank Haverkamp <haver@linux.ibm.com>
Cc: Frederic Barrat <fbarrat@linux.ibm.com>
Cc: John Allen <jallen@linux.ibm.com>
Cc: Manoj N. Kumar <manoj@linux.ibm.com>
Cc: Matthew R. Ochs <mrochs@linux.ibm.com>
Cc: Michael Cyr <mikecyr@linux.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Paulo Flabiano Smorigo <pfsmorigo@linux.ibm.com>
Cc: Philip Kelleher <pjk1939@linux.ibm.com>
Cc: Steven Royer <seroyer@linux.ibm.com>
Cc: Thomas Falcon <tlfalcon@linux.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>
Cc: Uma Krishnan <ukrishn@linux.ibm.com>
Acked-by: James Bottomley <jejb@linux.ibm.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>