powerpc/Makefile: CROSS32AS is unused, remove it

In fact it makes no sense at all to have this defined on little endian
builds. Since we disabled the 32-bit VDSO on little endian, we don't
build any 32-bit code when building a little endian kernel.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/Makefile

@@ -67,7 +67,6 @@ UTS_MACHINE := $(OLDARCH)
 
 ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
 override LD	+= -EL
-override CROSS32AS += -mlittle-endian
 LDEMULATION	:= lppc
 GNUTARGET	:= powerpcle
 MULTIPLEWORD	:= -mno-multiple