drm/amdgpu: expose AMDGPU_GEM_CREATE_VRAM_CLEARED to user space

V2: fix the return value for fill failure and validate bo before
filling data

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Flora Cui <Flora.Cui@amd.com>
Reviewed-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>