reset: Add driver for gpio-controlled reset pins

reset: Add driver for gpio-controlled reset pins

This driver implements a reset controller device that toggle a gpio
connected to a reset pin of a peripheral IC. The delay between assertion
and de-assertion of the reset signal can be configured via device tree.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
[shawn.guo: cherry-pick commit 27e3604c82cb from imx_3.10.y]
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Conflicts:
	drivers/reset/Makefile