Revert "lava: Prevent AUM tests to be generated for RPi board"

RPi AUM tests were disabled on Lava due to an issue on RPi4 U-boot.

The origin of this issue was that the same U-boot's defconfig
`rpi_arm64_defconfig` is used for both RPi3 and RPi4. This defconfig
sets the bootcount mmc dev/part to `0:1`. For RPi3 this works fine, as
mmc0 is the SD card, but on RPi4 mmc0 is used to control the SDIO for
wireless.

This has been fixed already by setting the aliases on RPi4 dtb for its
mmc devices. Thus, AUM tests can be re-enabled on RPi.

This reverts commit  4d06a3d1:

  Author: Frédéric Danis <frederic.danis@collabora.com>
  Date:   Wed Feb 16 17:07:05 2022 +0100

      lava: Prevent AUM tests to be generated for RPi board

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>