powerpc: Make powerpc pmac 32 bit build again

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
diff --git a/arch/powerpc/platforms/Makefile b/arch/powerpc/platforms/Makefile
index 697adde..7637ff3 100644
--- a/arch/powerpc/platforms/Makefile
+++ b/arch/powerpc/platforms/Makefile
@@ -1,4 +1,6 @@
+ifeq ($(CONFIG_PPC32),y)
 obj-$(CONFIG_PPC_PMAC)		+= powermac/
+endif
 obj-$(CONFIG_4xx)		+= 4xx/
 obj-$(CONFIG_83xx)		+= 83xx/
 obj-$(CONFIG_85xx)		+= 85xx/