s390: kernel: make lgr explicitly non-modular

The Makefile currently controlling compilation of this code is obj-y
meaning that it currently is not being built as a module by anyone.

Lets remove the couple traces of modular infrastructure use, so that
when reading the driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

We replace module.h with init.h and export.h since the file does
export some symbols.

Cc: [e-mail]
Signed-off-by: Paul Gortmaker <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/kernel/lgr.c

···
  * Author(s): Michael Holzheu <[e-mail]>
  */
 
-#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/export.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
 #include <asm/facility.h>
···
 	lgr_timer_set();
 	return 0;
 }
-module_init(lgr_init);
+device_initcall(lgr_init);