drm/nouveau: remove quirk to fabricate DVI-A output on DCB 1.5 boards

There's a report of this quirk breaking modesetting on at least one board.
After discussion with Francisco Jerez, we've decided to remove it:

<darktama> it's not worth limiting the quirk to just where we know it can
           work?  i'm happy either way really :)
<curro> hmm, don't think so, most if not all DCB15 cards have just one DAC
<curro> and with that quirk there's no way to tell if the load comes from
        the VGA or DVI port
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Francisco Jerez <currojerez@riseup.net>

drivers/gpu/drm/nouveau/nouveau_bios.c

@@ -5739,13 +5739,6 @@ parse_dcb15_entry(struct drm_device *dev, struct dcb_table *dcb,
 	case OUTPUT_TV:
 		entry->tvconf.has_component_output = false;
 		break;
-	case OUTPUT_TMDS:
-		/*
-		 * Invent a DVI-A output, by copying the fields of the DVI-D
-		 * output; reported to work by math_b on an NV20(!).
-		 */
-		fabricate_vga_output(dcb, entry->i2c_index, entry->heads);
-		break;
 	case OUTPUT_LVDS:
 		if ((conn & 0x00003f00) != 0x10)
 			entry->lvdsconf.use_straps_for_mode = true;