mailmap: add Mark Brown

A couple of commits have a broken real name - fix them up.
Signed-off-by: Mark Brown <broonie@sirena.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

.mailmap

@@ -66,6 +66,7 @@ Kenneth W Chen <kenneth.w.chen@intel.com>
 Koushik <raghavendra.koushik@neterion.com>
 Leonid I Ananiev <leonid.i.ananiev@intel.com>
 Linas Vepstas <linas@austin.ibm.com>
+Mark Brown <broonie@sirena.org.uk>
 Matthieu CASTET <castet.matthieu@free.fr>
 Michael Buesch <mb@bu3sch.de>
 Michael Buesch <mbuesch@freenet.de>