modules: Fix build error in moduleloader.h

Fengguang Wu's build bot detected that if moduleloader.h is included in
a C file (used by ftrace and kprobes to access module_alloc() when
available), that it can fail to build if CONFIG_MODULES and
CONFIG_MODULES_USE_ELF_REL is not defined.

This is because there's a printk() that dereferences struct module to
print the name of the module. But as struct module does not exist when
CONFIG_MODULES is not defined we get this error:

   include/linux/moduleloader.h: In function 'apply_relocate':
>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to
>> incomplete type
     printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
								  ^
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Based-on-the-true-story-by: Steven Rostedt <rostedt@goodmis.org>
Confirms-rustys-story-ends-the-same-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/moduleloader.h

@@ -45,7 +45,8 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
 				 unsigned int relsec,
 				 struct module *me)
 {
-	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
+	printk(KERN_ERR "module %s: REL relocation unsupported\n",
+	       module_name(me));
 	return -ENOEXEC;
 }
 #endif
@@ -67,7 +68,8 @@ static inline int apply_relocate_add(Elf_Shdr *sechdrs,
 				     unsigned int relsec,
 				     struct module *me)
 {
-	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
+	printk(KERN_ERR "module %s: REL relocation unsupported\n",
+	       module_name(me));
 	return -ENOEXEC;
 }
 #endif