MAINTAINERS: add bgmac section entry

This driver exists for years but was missing its MAINTAINERS entry.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210107180051.1542-3-zajec5@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -3660,6 +3660,15 @@ N:	bcm88312
 N:	hr2
 N:	stingray
 
+BROADCOM IPROC GBIT ETHERNET DRIVER
+M:	Rafał Miłecki <rafal@milecki.pl>
+M:	bcm-kernel-feedback-list@broadcom.com
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/net/brcm,amac.txt
+F:	drivers/net/ethernet/broadcom/bgmac*
+F:	drivers/net/ethernet/broadcom/unimac.h
+
 BROADCOM KONA GPIO DRIVER
 M:	Ray Jui <rjui@broadcom.com>
 L:	bcm-kernel-feedback-list@broadcom.com