power: Introduce Broadcom kona reset driver

This driver supports reset on both BCM21664 and BCM23550.
Code is being moved from arch/arm/mach-bcm/board_bcm21664.c

Signed-off-by: Chris Brand <chris.brand@broadcom.com>
Acked-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>