x86: don't use module_init in non-modular devicetree.c code

The devicetree.o is built for "OF" -- which is bool, and hence
this code is either present or absent.  It will never be modular,
so using module_init as an alias for __initcall can be somewhat
misleading.

Fix this up now, so that we can relocate module_init from
init.h into module.h in the future.  If we don't do this, we'd
have to add module.h to obviously non-modular code, and that
would be a worse thing.

Note that direct use of __initcall is discouraged, vs. one
of the priority categorized subgroups.  As __initcall gets
mapped onto device_initcall, our use of device_initcall
directly in this change means that the runtime impact is
zero -- it will remain at level 6 in initcall ordering.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

arch/x86/kernel/devicetree.c

@@ -65,7 +65,7 @@ static int __init add_bus_probe(void)
 
 	return of_platform_bus_probe(NULL, ce4100_ids, NULL);
 }
-module_init(add_bus_probe);
+device_initcall(add_bus_probe);
 
 #ifdef CONFIG_PCI
 struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus)