soc: imx: add i.MX8M blk-ctrl driver

This adds a driver for the blk-ctrl blocks found in the i.MX8M* line of
SoCs. The blk-ctrl is a top-level peripheral located in the various *MIX
power domains and interacts with the GPC power controller to provide the
peripherals in the power domain access to the NoC and ensures that those
peripherals are properly reset when their respective power domain is
brought back to life.

Software needs to do different things to make the bus handshake happen
after the GPC *MIX domain is powered up and before it is powered down.
As the requirements are quite different between the various blk-ctrls
there is a callback function provided to hook in the proper sequence.

The peripheral domains are quite uniform, they handle the soft clock
enables and resets in the blk-ctrl address space and sequencing with the
upstream GPC power domains.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/soc/imx/Makefile

@@ -5,3 +5,4 @@ endif
 obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
 obj-$(CONFIG_IMX_GPCV2_PM_DOMAINS) += gpcv2.o
 obj-$(CONFIG_SOC_IMX8M) += soc-imx8m.o
+obj-$(CONFIG_SOC_IMX8M) += imx8m-blk-ctrl.o