drm/radeon: add connector table for Mac G4 Silver

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>
Cc: stable@vger.kernel.org