rockchip: reset: support a (common) rockchip reset drivers

rockchip: reset: support a (common) rockchip reset drivers

Create driver to support the soft reset (i.e. peripheral)
of all Rockchip SoCs.

Example of usage:
i2c driver:
	ret = reset_get_by_name(dev, "i2c", &reset_ctl);
	if (ret) {
		error("reset_get_by_name() failed: %d\n", ret);
	}

	reset_assert(&reset_ctl);
	udelay(50);
	reset_deassert(&reset_ctl);

i2c dts node:
resets = <&cru SRST_P_I2C1>, <&cru SRST_I2C1>;
reset-names = "p_i2c", "i2c";

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
[Fixed commit tag:]
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>