drm/mgag200: Store HW_BUG_NO_STARTADD flag in device info

Flag devices with broken handling of the startadd field in
struct mgag200_device_info, instead of PCI driver data. This
reduces the driver data to a simple type constant.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220601112522.5774-8-tzimmermann@suse.de