drm/amdgpu: fix coding style in amdgpu_job_free

Ther should be a new line between code and decleration.
Also use amdgpu_ib_free() instead of releasing the member manually.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Monk.Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>