MAINTAINERS: Take over BCM2835 maintainership

It seems as if I have more interest in BCM2835 support than most others,
so I'll bite the bullet and declare myself maintainer. It'd be a shame
to leave that platform orphaned.

Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index af9965a..dd24697 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -92,8 +92,8 @@
 F:	arch/arm/mach-at91/
 
 ARM BROADCOM BCM283X
-#M:	Stephen Warren <swarren@wwwdotorg.org>
-S:	Orphaned (Since 2017-07)
+M:	Alexander Graf <agraf@suse.de>
+S:	Maintained
 F:	arch/arm/mach-bcm283x/
 F:	drivers/gpio/bcm2835_gpio.c
 F:	drivers/mmc/bcm2835_sdhci.c