reset: intel: Add system reset controller driver

Add driver for the reset controller present on Intel
Gateway SoCs for performing reset management of the
devices present on the SoC. Driver also registers a
reset handler to peform the entire device reset.

Signed-off-by: Dilip Kota <eswara.kota@linux.intel.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>