[POWERPC] Rename 4xx paths to 40x

4xx is a bit of a misnomer for certain things, as they really apply to PowerPC
40x only.  Rename some of the files to clean this up.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>

arch/powerpc/kernel/Makefile

@@ -46,7 +46,7 @@ ifeq ($(CONFIG_PPC_MERGE),y)
 
 extra-$(CONFIG_PPC_STD_MMU)	:= head_32.o
 extra-$(CONFIG_PPC64)		:= head_64.o
-extra-$(CONFIG_40x)		:= head_4xx.o
+extra-$(CONFIG_40x)		:= head_40x.o
 extra-$(CONFIG_44x)		:= head_44x.o
 extra-$(CONFIG_FSL_BOOKE)	:= head_fsl_booke.o
 extra-$(CONFIG_8xx)		:= head_8xx.o