Allow updating display with hardware SPI chip select

[thexa4]

I tried to get the display to work on base Debian Trixie, and I wasn't able to get the kernel to allow manually doing chip selection on the spi controller. It seems that software control of the chip select pin is not necessary, the spidev driver automatically uses the pin correctly. This PR disables the manual chipselect if the chipselect pin is under control of the spirit driver.

If you want to enable the spi device on Debian Trixie, use the following overlay: spi.dts

/dts-v1/;
/plugin/;

/ {
	compatible = "brcm,bcm2835";
};

&spi {
	status = "okay";

	spidev@0 {
		compatible = "rohm,dh2228fv";
		reg = <0>;
		status = "okay";
		spi-max-frequency = <100000>;
	};
};

• Make sure to have the compiler installed: apt install device-tree-compiler
• Then compile as follows: dtc -I dts -O dtb -o /boot/firmware/overlays/spi.dtbo spi.dts
• Add it to the config.txt: echo 'dtoverlay=spi' >> /etc/default/raspi-firmware-custom
• And update the boot partition: DEB_MAINT_PARAMS=configure /etc/kernel/postinst.d/z50-raspi-firmware