A note on lesson 3 SPI vs SPIM

[bscoventry]

This is just a note to update code and course to indicate that the custom board spi runs legacy spi, and not the more modern SPIM in Zephyr. To point:

&spi1 {
compatible = "nordic,nrf-spi";
status = "okay";
pinctrl-0 = <&spi1_default>;
pinctrl-1 = <&spi1_sleep>;
pinctrl-names = "default", "sleep";
};

needs to be changed to

&spi1 {
compatible = "nordic,nrf-spim";
status = "okay";
pinctrl-0 = <&spi1_default>;
pinctrl-1 = <&spi1_sleep>;
pinctrl-names = "default", "sleep";
};
To run correctly with the SPIM peripherial.