[Why]
Currently navy_flounder is using sienna_cichlid_dmcub.bin.

[How]
Create a seperate define so navy_flounder will use its own firmware.
Signed-off-by: NBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>