drm/amdgpu: declare ta firmware for navy_flounder

The firmware provided via MODULE_FIRMWARE appears in the
module information. External tools(eg. dracut) may use the
list of fw files to include them as appropriate in an initramfs,
thus missing declaration will lead to request firmware failure
in boot time.

Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Tianci Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>