Well those gpio_xyz are valid options for P9.13 → P9.16, and why your spi_xyz options failed…
Emulated/BitBang/etc… Manually toggling gpio pins to emulate spi bus, that’s exactly what the spi-gpio driver does… spi-gpio.c « spi « drivers - kernel/git/torvalds/linux.git - Linux kernel source tree
DeviceTree docs: spi-gpio.yaml « spi « bindings « devicetree « Documentation - kernel/git/torvalds/linux.git - Linux kernel source tree
Regards,