drm/nouveau/clk: Don't create cstates with voltages higher than what the gpu can do

nvkm_volt_map_min is a copy of nvkm_volt_map, which always returns the
lowest possible voltage for a cstate.

nvkm_volt_map will get a temperature parameter there later and also fix
the voltage calculation, so that this functions will be completly
different later.

Signed-off-by: Karol Herbst <karolherbst@gmail.com>
Reviewed-by: Martin Peres <martin.peres@free.fr>
Tested-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/volt.h

@@ -17,6 +17,7 @@ struct nvkm_volt {
 	u32 min_uv;
 };
 
+int nvkm_volt_map_min(struct nvkm_volt *volt, u8 id);
 int nvkm_volt_get(struct nvkm_volt *);
 int nvkm_volt_set_id(struct nvkm_volt *, u8 id, int condition);