MAINTAINERS: add RaspberryPi co-maintainer

Peter accpeted to step up as a co-maintainer for the RPis.
Reflect that in the corresponding MAINTAINERS files.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index bc9081b..f9f4eed 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -192,6 +192,7 @@
 
 ARM BROADCOM BCM283X / BCM27XX
 M:	Matthias Brugger <mbrugger@suse.com>
+M:	Peter Robinson <pbrobinson@gmail.com>
 S:	Maintained
 F:	arch/arm/dts/bcm283*
 F:	arch/arm/mach-bcm283x/