xtensa: 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/xtensa/boot/lib/Makefile b/arch/xtensa/boot/lib/Makefile
index d3d2aa2..ad8952e 100644
--- a/arch/xtensa/boot/lib/Makefile
+++ b/arch/xtensa/boot/lib/Makefile
@@ -6,7 +6,7 @@
 
 lib-y	+= $(zlib:.c=.o) zmem.o
 
-EXTRA_CFLAGS	+= -Ilib/zlib_inflate
+ccflags-y	:= -Ilib/zlib_inflate
 
 quiet_cmd_copy_zlib = COPY    $@
       cmd_copy_zlib = cat $< > $@