Add amdgpu_amdkfd_ prefix to amdgpu functions served for amdkfd usage.

v2: fix indentation
Signed-off-by: NAmber Lin <Amber.Lin@amd.com>
Acked-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>