test_hardware: Use (new) static SPI bus numbers

[hnez]

The SPI bus order has seemingly shifted by one position with the update to kernel 6.11, resulting in the following build errors:

05:45:11 FAILED tests/test_linux_hardware.py::test_linux_spi_1_adc - labgrid.driver.exception.ExecutionError: ('cat /sys/bus/spi/devices/spi1.0/iio\\:device3/in_voltage_raw', ["cat: '/sys/bus/spi/devices/spi1.0/iio:device3/in_voltage_raw': No such file or directory"], [])
05:45:11 FAILED tests/test_linux_hardware.py::test_linux_spi_2_lcd - labgrid.driver.exception.ExecutionError: ('cat /sys/bus/spi/devices/spi2.0/graphics/fb0/name', ['cat: /sys/bus/spi/devices/spi2.0/graphics/fb0/name: No such file or directory'], [])

I've marked this PR as a draft since just adapting to the new order and hoping that it does not change again is a bit of a hack.
We should check first if we can make the bus number assignment stable before we change it here.

[marckleinebudde]

As you already suggested, better use DT aliases:

https://elixir.bootlin.com/linux/v6.11.5/source/arch/arm/boot/dts/st/stm32mp157a-stinger96.dtsi#L15

[hnez]

I've prepared a pull request to set fixed SPI bus numbers via aliases: linux-automation/meta-lxatac#205 .

With this PR applied the bus number associations are the following:

Linux bus number	STM32 SPI peripheral	Connected Peripherals
0	2	Power Board ADC
1	4	LCD Display
2	5	Ethernet Switch

E.g. order the Linux bus numbers based on the STM32 peripheral numbers and leave out unused peripherals.

This new numbering matches the numbering introduced in this labgrid-lxatac PR.

So we should thus merge both:

• meta-lxatac-bsp: linux-lxatac: add aliases for can/i2c/spi and disable rtc meta-lxatac#205 and
• test_hardware: Use (new) static SPI bus numbers #4 (this PR)