Add RS485 mode support for UART2, UART3, UART4, and UART5.#6820

pelwell merged 2 commits intoraspberrypi:rpi-6.12.yraspberrypi/linux:rpi-6.12.yfrom

TheMightyMadman:add_rs485modeTheMightyMadman/linux:add_rs485modeCopy head branch name to clipboard