drm/nouveau: fix pramdac_table range checking

get_tmds_index_reg reads some value from stack when mlv happens
to be equal to size of pramdac_table array. Fix it.
Reported-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: NFrancisco Jerez <currojerez@riseup.net>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bios.c

@@ -762,7 +762,7 @@ static uint32_t get_tmds_index_reg(struct drm_device *dev, uint8_t mlv)
 			dacoffset ^= 8;
 		return 0x6808b0 + dacoffset;
 	} else {
-		if (mlv > ARRAY_SIZE(pramdac_table)) {
+		if (mlv >= ARRAY_SIZE(pramdac_table)) {
 			NV_ERROR(dev, "Magic Lookup Value too big (%02X)\n",
 									mlv);
 			return 0;