arm: don't use module_init in non-modular mach-vexpress/spc.c code

The spc.o is built for ARCH_VEXPRESS_SPC -- 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.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

arch/arm/mach-vexpress/spc.c

@@ -589,4 +589,4 @@ static int __init ve_spc_clk_init(void)
 	platform_device_register_simple("vexpress-spc-cpufreq", -1, NULL, 0);
 	return 0;
 }
-module_init(ve_spc_clk_init);
+device_initcall(ve_spc_clk_init);