unify HOST_CFLAGS and HOSTCFLAGS

The top build system sets up HOSTCFLAGS a bit and exports it, but other
places use HOST_CFLAGS instead.  Unify the two as HOSTCFLAGS so that the
values stay in sync.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/cpu/ixp/npe/Makefile b/cpu/ixp/npe/Makefile
index f4f97bd..8fefd29 100644
--- a/cpu/ixp/npe/Makefile
+++ b/cpu/ixp/npe/Makefile
@@ -27,7 +27,7 @@
 
 LOCAL_CFLAGS  += -I$(TOPDIR)/cpu/ixp/npe/include -DCONFIG_IXP425_COMPONENT_ETHDB -D__linux
 CFLAGS  += $(LOCAL_CFLAGS)
-HOST_CFLAGS  += $(LOCAL_CFLAGS)
+HOSTCFLAGS  += $(LOCAL_CFLAGS)
 
 COBJS-$(CONFIG_IXP4XX_NPE) := npe.o \
 	miiphy.o \