drm/nouveau/gm107: add voltage control using the new gk104 volt class

Let's ignore the other desktop Maxwells until I get my hands on one and confirm
that we still can change the voltage.
Signed-off-by: Martin Peres <martin.peres@free.fr>

drivers/gpu/drm/nouveau/nvkm/engine/device/base.c

@@ -1952,6 +1952,7 @@ nv117_chipset = {
 	.pmu = gm107_pmu_new,
 	.therm = gm107_therm_new,
 	.timer = gk20a_timer_new,
+	.volt = gk104_volt_new,
 	.ce[0] = gk104_ce_new,
 	.ce[2] = gk104_ce_new,
 	.disp = gm107_disp_new,