soc: imx: Add GPCv2 power gating driver

Add code allowing for control of various power domains managed by GPCv2
IP block found in i.MX7 series of SoCs. Power domains covered by this
patch are:

    - PCIE PHY
    - MIPI PHY
    - USB HSIC PHY
    - USB OTG1/2 PHY

Support for any other power domain controlled by GPC is not present, and
can be added at some later point.

Testing of this code was done against a PCIe driver.

Cc: yurovsky@gmail.com
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Dong Aisheng <dongas86@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
diff --git a/drivers/soc/imx/Kconfig b/drivers/soc/imx/Kconfig
new file mode 100644
index 0000000..357a5d8
--- /dev/null
+++ b/drivers/soc/imx/Kconfig
@@ -0,0 +1,9 @@
+menu "i.MX SoC drivers"
+
+config IMX7_PM_DOMAINS
+	bool "i.MX7 PM domains"
+	select PM_GENERIC_DOMAINS
+	depends on SOC_IMX7D || (COMPILE_TEST && OF)
+	default y if SOC_IMX7D
+
+endmenu