m68k: coldfire/5441x: register mcf-rcm-reset platform device

Add SoC-level registration of the mcf-rcm-reset platform device so the
power_on_reason sysfs attribute is created on every MCF5441x board
without per-board boilerplate.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>