[PATCH] symbol_get linkage fix

Patch from Rusty Russell <rusty@rustcorp.com.au>

Make symbol_get() use undefined weak symbols if !CONFIG_MODULE.
Many thanks to RTH for introducing undef weak symbols to me.

include/linux/module.h

@@ -344,7 +344,7 @@ static inline int module_text_address(unsigned long addr)
 }
 
 /* Get/put a kernel symbol (calls should be symmetric) */
-#define symbol_get(x) (&(x))
+#define symbol_get(x) ({ extern typeof(x) x __attribute__((weak)); &(x); })
 #define symbol_put(x) do { } while(0)
 #define symbol_put_addr(x) do { } while(0)