x86: add the RDC machine specific reboot fixup

The RDC R-321x SoC needs a reboot fixup which
uses its internal hardware watchdog set to
reset the CPU on next tick.

Signed-off-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>