[POWERPC] iSeries: stop dt_mod.o being rebuilt unnecessarily

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/iseries/Makefile

 EXTRA_CFLAGS	+= -mno-minimal-toc
 
+extra-y += dt.o
+
 obj-y += hvlog.o hvlpconfig.o lpardata.o setup.o dt_mod.o mf.o lpevents.o \
 	hvcall.o proc.o htab.o iommu.o misc.o irq.o
 obj-$(CONFIG_PCI) += pci.o vpdinfo.o
@@ -7,5 +9,9 @@ obj-$(CONFIG_SMP) += smp.o
 obj-$(CONFIG_VIOPATH) += viopath.o
 obj-$(CONFIG_MODULES) += ksyms.o
 
+quiet_cmd_dt_strings = DT_STR  $@
+      cmd_dt_strings = $(OBJCOPY) --rename-section .rodata.str1.8=.dt_strings \
+				$< $@
+
 $(obj)/dt_mod.o:	$(obj)/dt.o
-	@$(OBJCOPY) --rename-section .rodata.str1.8=.dt_strings $(obj)/dt.o $(obj)/dt_mod.o
+	$(call if_changed,dt_strings)