mips: 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>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/arch/mips/jz4740/Makefile b/arch/mips/jz4740/Makefile
index a604eae..a9dff33 100644
--- a/arch/mips/jz4740/Makefile
+++ b/arch/mips/jz4740/Makefile
@@ -17,4 +17,4 @@
 
 obj-$(CONFIG_PM) += pm.o
 
-EXTRA_CFLAGS += -Werror -Wall
+ccflags-y := -Werror -Wall