drm/nouveau/clk/gk20a: only compute n_lo if needed

n_lo is used if we are going to slide. Compute it only if that condition
succeeds to avoid confusion about future usage of this computation.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
1 file changed