drm/amdgpu: remove needless usage of #ifdef

define sched_policy in case CONFIG_HSA_AMD is not
enabled, with this there is no need to check for CONFIG_HSA_AMD
else where in driver code.

Suggested-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>