MAINTAINERS: add a third maintainer to mach-bcm

Add myself as a third maintainer to the mach-bcm code to increase the
chances the redundancy in the merging/reviewing process.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Scott Branden <sbranden@broadcom.com>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>