drm/amdkfd: Delete unnecessary function declarations

Ajust the function sequences so that those function delcarations are not
needed any more.

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>