Introduce arch_phys_memset which works like memset but on physical memory

The default implementation of this function is just memset, but other
implementations will be needed when physical memory isn't accessible by
U-Boot using normal addressing mechanisms.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Makefile b/lib/Makefile
index e44e045..f83f6e8 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -48,6 +48,7 @@
 COBJS-y += ldiv.o
 COBJS-$(CONFIG_MD5) += md5.o
 COBJS-y += net_utils.o
+COBJS-$(CONFIG_PHYSMEM) += physmem.o
 COBJS-y += qsort.o
 COBJS-$(CONFIG_SHA1) += sha1.o
 COBJS-$(CONFIG_SHA256) += sha256.o