arm, suen3: fix compile error, if doing not a local build

Signed-off-by: Heiko Schocher <hs@denx.de>

board/keymile/km_arm/Makefile

@@ -23,6 +23,9 @@
 #
 
 include $(TOPDIR)/config.mk
+ifneq ($(OBJTREE),$(SRCTREE))
+$(shell mkdir -p $(obj)../common)
+endif
 
 LIB	= $(obj)lib$(BOARD).a