net: wan: wanxl: define CROSS_COMPILE_M68K

It was used but never set.  The hardcoded value from before the dawn of
time was non-standard; the usual name for cross-tools is $TRIPLET-$TOOL

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wan/Makefile b/drivers/net/wan/Makefile
index f6b92eff..480bcd1 100644
--- a/drivers/net/wan/Makefile
+++ b/drivers/net/wan/Makefile
@@ -34,6 +34,8 @@
 clean-files := wanxlfw.inc
 $(obj)/wanxl.o:	$(obj)/wanxlfw.inc
 
+CROSS_COMPILE_M68K = m68k-linux-gnu-
+
 ifeq ($(CONFIG_WANXL_BUILD_FIRMWARE),y)
 ifeq ($(ARCH),m68k)
   M68KCC = $(CC)