Add devicetree runtime modification support for continious flashing

[zaolin]

Hi,

we need to add a script for flashing which should enable and disable dynamically gpio on use (CLK, CS, GND, VCC) to improve better flashing and debugging experience.

[lynxis]

I'm testing this on a debian based image, when it's working, we need also to port the capemgmt to openwrt.

/dts-v1/;
/plugin/;

/ {
    compatible = "ti,beaglebone", "ti,beaglebone-black";

    fragment@0 {
        target = <&spi0>;
        __overlay__ {
            status = "disabled";
        };

    fragment@1 {
        target = <&am33xx_pinmux>;
        __overlay__ {
            pinctrl_spi0: pinctrl_spi1_pins {
                pinctrl-single,pins = <                                        
                    0x150 (PIN_INPUT | MUX_MODE7)    /* spi0_sclk */
                    0x154 (PIN_INPUT | MUX_MODE7)    /* spi0_d0 */
                    0x158 (PIN_INPUT | MUX_MODE7)   /* spi0_d1 */
                    0x15c (PIN_INPUT | MUX_MODE7)   /* spi0_cs0 */
                >;
            };
        };
    };
};