drm/amd/amdgpu: add rlc_firmware_header_v2_4 to amdgpu_firmware_header

Add missing structure to avoid incorrect size and version check.

Signed-off-by: Chengming Gui <Jack.Gui@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>