drm/amdgpu/pm: Fix the param type of set_power_profile_mode

Function .set_power_profile_mode need an array as input
parameter. So define variable workload as an array to fix
the below coverity warning.

"Passing &workload to function hwmgr->hwmgr_func->set_power_profile_mode
which uses it as an array. This might corrupt or misinterpret adjacent
memory locations"

Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>