powerpc: Don't use ELFv2 ABI to build the kernel

The kernel doesn't build correctly using the ELFv2 ABI.  This patch
ensures that the ELFv1 ABI is used when building a kernel with an
ELFv2 enabled compiler.
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Makefile

@@ -111,6 +111,7 @@ endif
 endif
 
 CFLAGS-$(CONFIG_PPC64)	:= -mtraceback=no -mcall-aixdesc
+CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mabi=elfv1)
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mcmodel=medium,-mminimal-toc)
 CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mno-pointers-to-nested-functions)
 CFLAGS-$(CONFIG_PPC32)	:= -ffixed-r2 $(MULTIPLEWORD)