MAINTAINERS: add entry for the GISB arbiter driver

The GISB bus arbiter driver is relevant for BCM7xxx (brcmstb) platforms,
add an entry to cover this file.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

diff --git a/MAINTAINERS b/MAINTAINERS
index 7bbca94..d45abb1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2093,6 +2093,7 @@
 S:	Maintained
 F:	arch/arm/mach-bcm/*brcmstb*
 F:	arch/arm/boot/dts/bcm7*.dts*
+F:	drivers/bus/brcmstb_gisb.c
 
 BROADCOM TG3 GIGABIT ETHERNET DRIVER
 M:	Prashant Sreedharan <prashant@broadcom.com>