ima3-mx53: Remove unused SOBJS

There is no .S file in this directory, so just remove SOBJS.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/board/esg/ima3-mx53/Makefile b/board/esg/ima3-mx53/Makefile
index f3b13bc..ab18944 100644
--- a/board/esg/ima3-mx53/Makefile
+++ b/board/esg/ima3-mx53/Makefile
@@ -25,7 +25,7 @@
 
 COBJS	:= ima3-mx53.o
 
-SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
+SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))
 
 $(LIB):	$(obj).depend $(OBJS)