MAINTAINERS: drop bcm283x/rpi maintainership

It's been a while since I've touched U-Boot on the Raspberry Pi and
other things have been taking my time. Drop my maintainership for this
port.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 4e41455..1e8d7d9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -78,8 +78,8 @@
 F:	arch/arm/mach-at91/
 
 ARM BROADCOM BCM283X
-M:	Stephen Warren <swarren@wwwdotorg.org>
-S:	Maintained
+#M:	Stephen Warren <swarren@wwwdotorg.org>
+S:	Orphaned (Since 2017-07)
 F:	arch/arm/mach-bcm283x/
 F:	drivers/gpio/bcm2835_gpio.c
 F:	drivers/mmc/bcm2835_sdhci.c