virtual display is enabled unconditionally in SR-IOV, but
without specifying the virtual_display module, the number
of crtcs defaults to 0.  Set a single display by default
for SR-IOV if the virtual_display parameter is not set.
Only enable virtual display by default on SR-IOV on asics
which actually have display hardware.
Acked-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>