Only load the SDMA0/MEC1 firmware once in the Carrizo SMU manager
driver.

(v2) Avoid loading SDMA0 twice too.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>