drm/nouveau/clk: Let nvkm_clk_tstate take a temperature value

This way other subdevs can notify the clk subdev about temperature changes
without the need of clk to poll that value.

Also make this function safe to be called from an interrupt handler.

Signed-off-by: Karol Herbst <karolherbst@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>