ixp/npe: Move conditional compilation to Makefile

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/cpu/ixp/npe/Makefile b/cpu/ixp/npe/Makefile
index 25117d7..aa664a1 100644
--- a/cpu/ixp/npe/Makefile
+++ b/cpu/ixp/npe/Makefile
@@ -29,7 +29,7 @@
 CFLAGS  += $(LOCAL_CFLAGS)
 HOST_CFLAGS  += $(LOCAL_CFLAGS)
 
-COBJS := npe.o \
+COBJS-$(CONFIG_IXP4XX_NPE) := npe.o \
 	miiphy.o \
 	IxOsalBufferMgt.o \
 	IxOsalIoMem.o \
@@ -80,16 +80,16 @@
 	IxNpeMhUnsolicitedCbMgr.o
 
 ifndef CONFIG_IXP4XX_NPE_EXT_UCODE_BASE
-COBJS += IxNpeMicrocode.o
+COBJS-$(CONFIG_IXP4XX_NPE) += IxNpeMicrocode.o
 endif
 
-SRCS	:= $(START:.o=.S) $(SOBJS:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))
-START	:= $(addprefix $(obj),$(START))
+SRCS	:= $(SOBJS:.o=.S) $(COBJS-y:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS-y))
+SOBJS	:= $(addprefix $(obj),$(SOBJS))
 
 all:	$(LIB)
 
-$(LIB):	$(OBJS)
+$(LIB):	$(obj).depend $(OBJS)
 	$(AR) $(ARFLAGS) $@ $(OBJS)
 
 #########################################################################
diff --git a/cpu/ixp/npe/npe.c b/cpu/ixp/npe/npe.c
index bd77fed..03e3bf7 100644
--- a/cpu/ixp/npe/npe.c
+++ b/cpu/ixp/npe/npe.c
@@ -44,8 +44,6 @@
 
 #include <npe.h>
 
-#ifdef CONFIG_IXP4XX_NPE
-
 static IxQMgrDispatcherFuncPtr qDispatcherFunc = NULL;
 static int npe_exists[NPE_NUM_PORTS];
 static int npe_used[NPE_NUM_PORTS];
@@ -690,5 +688,3 @@
 
 	return 1;
 }
-
-#endif /* CONFIG_IXP4XX_NPE */