MAINTAINERS: Update Paul Burton's email address

MAINTAINERS: Update Paul Burton's email address

Update my email address from paul.burton@imgtec.com to
paul.burton@mips.com, since MIPS will soon no longer be a part of
Imagination Technologies & as such the @imgtec.com address will soon
cease to function.

A mapping is added in .mailmap such that git reports the new @mips.com
address, and get_maintainer.pl in turn reports it when examining git
history. Whilst here add a mapping for my also-defunct
paul@archlinuxmips.org email address too.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Laurent Vivier <laurent@vivier.eu>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Cc: Yongbok Kim <yongbok.kim@imgtec.com>
Cc: Yongbok Kim <yongbok.kim@mips.com>
Cc: qemu-devel@nongnu.org
Cc: qemu-trivial@nongnu.org
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[Yongbok Kim:
  Updated message subject]
Signed-off-by: Yongbok Kim <yongbok.kim@imgtec.com>