tpm/st33zp24/dts/st33zp24-spi: Add dts documentation for st33zp24 spi phy

* STMicroelectronics SAS. ST33ZP24 TPM SoC

Required properties:

- compatible: Should be "st,st33zp24-spi".

- spi-max-frequency: Maximum SPI frequency (<= 10000000).

Optional ST33ZP24 Properties:

- interrupt-parent: phandle for the interrupt gpio controller

- interrupts: GPIO interrupt to which the chip is connected

- lpcpd-gpios: Output GPIO pin used for ST33ZP24 power management D1/D2 state.

If set, power must be present when the platform is going into sleep/hibernate mode.

Optional SoC Specific Properties:

- pinctrl-names: Contains only one value - "default".

- pintctrl-0: Specifies the pin control groups used for this controller.

Example (for ARM-based BeagleBoard xM with ST33ZP24 on SPI4):

&mcspi4 {

        status = "okay";

        st33zp24@0 {

                compatible = "st,st33zp24-spi";

                spi-max-frequency = <10000000>;

                interrupt-parent = <&gpio5>;

                interrupts = <7 IRQ_TYPE_LEVEL_HIGH>;

                lpcpd-gpios = <&gpio5 15 GPIO_ACTIVE_HIGH>;

        };

};