sh: Add -Werror for clean directories.

Follow the MIPS and sparc64 changes for -Werror instrumentation.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/oprofile/Makefile b/arch/sh/oprofile/Makefile
index 1f25d9b..2efc2e7 100644
--- a/arch/sh/oprofile/Makefile
+++ b/arch/sh/oprofile/Makefile
@@ -15,3 +15,4 @@
 
 oprofile-y				:= $(DRIVER_OBJS) $(profdrvr-y)
 
+EXTRA_CFLAGS += -Werror