net: change to new flag variable

Replace EXTRA_CFLAGS with ccflags-y.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/drivers/net/caif/Makefile b/drivers/net/caif/Makefile
index b38d987..9560b9d 100644
--- a/drivers/net/caif/Makefile
+++ b/drivers/net/caif/Makefile
@@ -1,6 +1,4 @@
-ifeq ($(CONFIG_CAIF_DEBUG),y)
-EXTRA_CFLAGS += -DDEBUG
-endif
+ccflags-$(CONFIG_CAIF_DEBUG) := -DDEBUG
 
 # Serial interface
 obj-$(CONFIG_CAIF_TTY) += caif_serial.o