MAINTAINERS: mpc83xx: Add new custodian

Add myself as mpc83xx custodian.
diff --git a/MAINTAINERS b/MAINTAINERS
index 56dd1f3..3c7438d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -340,8 +340,8 @@
 F:	arch/powerpc/cpu/mpc82*/
 
 POWERPC MPC83XX
-#M:	Kim Phillips <kim.phillips@freescale.com>
-S:	Orphaned (Since 2016-02)
+M:	Mario Six <mario.six@gdsys.cc>
+S:	Maintained
 T:	git git://git.denx.de/u-boot-mpc83xx.git
 F:	arch/powerpc/cpu/mpc83xx/
 F:	arch/powerpc/include/asm/arch-mpc83xx/