dt-bindings: fsl: add imx7ulp pm related components bindings

Add imx7ulp pm related components bindings.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Documentation/devicetree/bindings/arm/freescale/fsl,imx7ulp-pm.txt

+Freescale i.MX7ULP Power Management Components
+----------------------------------------------
+
+The Multi-System Mode Controller (MSMC) is responsible for sequencing
+the MCU into and out of all stop and run power modes. Specifically, it
+monitors events to trigger transitions between power modes while
+controlling the power, clocks, and memories of the MCU to achieve the
+power consumption and functionality of that mode.
+
+The WFI or WFE instruction is used to invoke a Sleep, Deep Sleep or
+Standby modes for either Cortex family. Run, Wait, and Stop are the
+common terms used for the primary operating modes of Kinetis
+microcontrollers.
+
+Required properties:
+- compatible:	Should be "fsl,imx7ulp-smc1".
+- reg:		Specifies base physical address and size of the register sets.
+
+Example:
+smc1: smc1@40410000 {
+	compatible = "fsl,imx7ulp-smc1";
+	reg = <0x40410000 0x1000>;
+};