mailmap: Add Bruce Fields' latest e-mail addresses

Ensure that Bruce's old e-mail addresses map to his current one so
he doesn't miss out on all the fun.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

.mailmap

@@ -181,6 +181,8 @@ Henrik Rydberg <rydberg@bitmath.org>
 Herbert Xu <herbert@gondor.apana.org.au>
 Huacai Chen <chenhuacai@kernel.org> <chenhc@lemote.com>
 Huacai Chen <chenhuacai@kernel.org> <chenhuacai@loongson.cn>
+J. Bruce Fields <bfields@fieldses.org> <bfields@redhat.com>
+J. Bruce Fields <bfields@fieldses.org> <bfields@citi.umich.edu>
 Jacob Shin <Jacob.Shin@amd.com>
 Jaegeuk Kim <jaegeuk@kernel.org> <jaegeuk@google.com>
 Jaegeuk Kim <jaegeuk@kernel.org> <jaegeuk.kim@samsung.com>