MIPS: FW: Build with -Werror

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/fw/arc/Makefile b/arch/mips/fw/arc/Makefile
index 4f349ec..e0aaad4 100644
--- a/arch/mips/fw/arc/Makefile
+++ b/arch/mips/fw/arc/Makefile
@@ -8,3 +8,5 @@
 lib-$(CONFIG_ARC_MEMORY)	+= memory.o
 lib-$(CONFIG_ARC_CONSOLE)	+= arc_con.o
 lib-$(CONFIG_ARC_PROMLIB)	+= promlib.o
+
+EXTRA_CFLAGS			+= -Werror