MAINTAINERS: Remove Blue Swirl leftovers

Blue hasn't been active in the QEMU project for a long time.  Drop his
last MAINTAINERS entries.

As per Paolo's recommendation, downgrade status of "BSD user" from
Maintained to Orphan since the FreeBSD guys effectively forked it, and
"SPARC target" from Maintained to Odd Fixes, since we still have the
overall TCG maintainer looking after it.

I'm leaving Checkpatch's status at Odd Fixes.  Calling it Maintained
wouldn't be wrong, but I'm not comfortable upgrading it while nobody
is willing to have his name nailed to the thing.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>