MIPS: BCM47xx: Migrate to new platform makefile style.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Kbuild.platforms b/arch/mips/Kbuild.platforms
index d99704c..e4c991e 100644
--- a/arch/mips/Kbuild.platforms
+++ b/arch/mips/Kbuild.platforms
@@ -2,6 +2,7 @@
 
 platforms += alchemy
 platforms += ar7
+platforms += bcm47xx
 platforms += cobalt
 platforms += dec
 platforms += jazz