drm/amdgpu: revert "Add a parameter to amdgpu_bo_create()"

This reverts commit 2046d46d.

Not needed any more.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>