MAINTAINERS: add brcm tag driver to b53

The b53 entry was missing the brcm tag driver, so add it.

Reported-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/netdev/20251029181216.3f35f8ba@kernel.org/
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20251101103954.29816-1-jonas.gorski@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: KanjiMonster

MAINTAINERS

@@ -4818,6 +4818,7 @@ F:	drivers/net/dsa/b53/*
 F:	drivers/net/dsa/bcm_sf2*
 F:	include/linux/dsa/brcm.h
 F:	include/linux/platform_data/b53.h
+F:	net/dsa/tag_brcm.c
 
 BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE
 M:	Florian Fainelli <florian.fainelli@broadcom.com>