powerpc: Fix build dependencies for epapr.c which needs libfdt.h

Currently, the build can (very rarely) fail to build because libfdt.h has
not been created or is in the process of being copied.

Signed-off-by: Matthew McClintock <msm@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index c26200b..ac6705e 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -58,7 +58,7 @@
 libfdt       := fdt.c fdt_ro.c fdt_wip.c fdt_sw.c fdt_rw.c fdt_strerror.c
 libfdtheader := fdt.h libfdt.h libfdt_internal.h
 
-$(addprefix $(obj)/,$(libfdt) libfdt-wrapper.o simpleboot.o): \
+$(addprefix $(obj)/,$(libfdt) libfdt-wrapper.o simpleboot.o epapr.o): \
 	$(addprefix $(obj)/,$(libfdtheader))
 
 src-wlib := string.S crt0.S crtsavres.S stdio.c main.c \