drm/amd/display: Add bios firmware info version for VG12

VG12 shows minor revision version of 2 which is not handled in
bios_parser_get_firmware_info() routine.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>