drm/amd/display: Rename firmware_info to dc_firmware_info

This is to avoid conflicts with amdgpu's firmware_info once we
merge amdgpu_dm_types with amdgpu_dm.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>