checkpatch: update MAINTAINERS entry

Update my email address to my new work address.  Also, as per our recent
email conversation remove Randy and Joel from the maintainers list.
Finally add LKML so that emails are recorded somewhere.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>