drm/amdgpu: fix fw attestation for MP0_14_0_{2/3}

FW attestation was disabled on MP0_14_0_{2/3}.

V2:
Move check into is_fw_attestation_support func. (Frank)
Remove DRM_WARN log info. (Alex)
Fix format. (Christian)

Signed-off-by: Gui Chengming <Jack.Gui@amd.com>
Reviewed-by: Frank.Min <Frank.Min@amd.com>
Reviewed-by: Christian König <Christian.Koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>