MAINTAINERS: Remove self as ARM mach-bcm co-maintainer

Removing myself as a co-maintainer.
Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -2107,7 +2107,6 @@ F:	drivers/net/ethernet/broadcom/bnx2x/
 
 BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITECTURE
 M:	Christian Daudt <bcm@fixthebug.org>
-M:	Matt Porter <mporter@linaro.org>
 M:	Florian Fainelli <f.fainelli@gmail.com>
 L:	bcm-kernel-feedback-list@broadcom.com
 T:	git git://github.com/broadcom/mach-bcm