drm/nouveau/imem/tu106: initial support

Appears to be compatible with NV50.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

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

@@ -2476,6 +2476,7 @@ nv166_chipset = {
 	.gpio = gk104_gpio_new,
 	.i2c = gm200_i2c_new,
 	.ibus = gm200_ibus_new,
+	.imem = nv50_instmem_new,
 	.mc = tu104_mc_new,
 	.pci = gp100_pci_new,
 	.timer = gk20a_timer_new,