IB: Replace EXTRA_CFLAGS with ccflags-y

Signed-off-by: matt mooney <mfm@muteddisk.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/cxgb4/Makefile b/drivers/infiniband/hw/cxgb4/Makefile
index e31a499..cd20b13 100644
--- a/drivers/infiniband/hw/cxgb4/Makefile
+++ b/drivers/infiniband/hw/cxgb4/Makefile
@@ -1,4 +1,4 @@
-EXTRA_CFLAGS += -Idrivers/net/cxgb4
+ccflags-y := -Idrivers/net/cxgb4
 
 obj-$(CONFIG_INFINIBAND_CXGB4) += iw_cxgb4.o