x86: include proper prototypes for rodata_test

extern should not appear in C files.  Also, the definitions
do not match the prototype currently, not sure what way you
want to go with this, I've switched the prototype to return
int, but I can see going to the void return as well.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/cacheflush.h b/include/asm-x86/cacheflush.h
index 6a22212..5396c21 100644
--- a/include/asm-x86/cacheflush.h
+++ b/include/asm-x86/cacheflush.h
@@ -48,12 +48,15 @@
 
 #ifdef CONFIG_DEBUG_RODATA
 void mark_rodata_ro(void);
+extern const int rodata_test_data;
 #endif
+
 #ifdef CONFIG_DEBUG_RODATA_TEST
-void rodata_test(void);
+int rodata_test(void);
 #else
-static inline void rodata_test(void)
+static inline int rodata_test(void)
 {
+	return 0;
 }
 #endif