ia64:unwind: fix double free for mod->arch.init_unw_table

The function free_module in file kernel/module.c as follow:

void free_module(struct module *mod) {
	......
	module_arch_cleanup(mod);
	......
	module_arch_freeing_init(mod);
	......
}

Both module_arch_cleanup and module_arch_freeing_init function
would free the mod->arch.init_unw_table, which cause double free.

Here, set mod->arch.init_unw_table = NULL after remove the unwind
table to avoid double free.

Signed-off-by: chenzefeng <chenzefeng2@huawei.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/module.c

@@ -914,10 +914,14 @@ module_finalize (const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *mo
 void
 module_arch_cleanup (struct module *mod)
 {
-	if (mod->arch.init_unw_table)
+	if (mod->arch.init_unw_table) {
 		unw_remove_unwind_table(mod->arch.init_unw_table);
-	if (mod->arch.core_unw_table)
+		mod->arch.init_unw_table = NULL;
+	}
+	if (mod->arch.core_unw_table) {
 		unw_remove_unwind_table(mod->arch.core_unw_table);
+		mod->arch.core_unw_table = NULL;
+	}
 }
 
 void *dereference_module_function_descriptor(struct module *mod, void *ptr)