drm/radeon: add connector table for Mac G4 Silver

commit cafa59b9011a7790be4ddd5979419259844a165d upstream.

Apple cards do not provide data tables in the vbios
so we have to hard code the connector parameters
in the driver.

Reported-by: Albrecht Dreß <albrecht.dress@arcor.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>