sh: convert processor device setup functions to arch_initcall()

Convert the processor platform device setup
functions from __initcall() and sometimes
device_initcall() to arch_initcall().

This makes sure that the platform devices are
registered a bit earlier so the devices are
available when drivers register using initcall
levels earlier than device_initcall().

A good example is platform devices needed by
i2c-sh_mobile.c which registers a bit earlier
using subsys_initcall().

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>