We shouldn't set voltages below the min or above the max voltage the gpu is
able to set, so save the range for future lookups.
Signed-off-by: Karol Herbst <karolherbst@gmail.de>
Reviewed-by: Martin Peres <martin.peres@free.fr>
Tested-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>