m68k: add the virtio devices aliases

m68k: add the virtio devices aliases

Similarly to 5f629d943cb0 ("s390x: fix s390 virtio aliases"),
define the virtio aliases.

This allows to start machines with virtio devices without
knowledge of the implementation type.

For instance, we can use "-device virtio-scsi" on
m68k, s390x or PC, and the device will be respectively
"virtio-scsi-device", "virtio-scsi-ccw" or "virtio-scsi-pci".

This already exists for s390x and -ccw interfaces, add them
for m68k and MMIO (-device) interfaces.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20210319202335.2397060-3-laurent@vivier.eu>
Message-Id: <20210323165308.15244-18-alex.bennee@linaro.org>