CI: Add m68k target

Add M5208EVBE board to CI. This does not use default config due to
limitations of QEMU emulation, instead the timer is switched from
DMA timer to PIT timer and RAMBAR accesses are inhibited.

Local QEMU launch command is as follows:
$ qemu-system-m68k -nographic -machine mcf5208evb -cpu m5208 -bios u-boot.bin

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Acked-by: Angelo Dureghello <angelo@kernel-space.org>