drm/i915: drop TVclock special casing on ilk+

TV-out uses the same reference clock as everyone else. The only
difference seems to be in the slightly different CB tuning limit.

Note that PLL_REF_INPUT_TVCLKINBC is a reserved value on ilk+. Also
strictly speaking we don't support native TV-out on ilk+, hence all
that code is dead. But Bspec still contains some residual mentions of
native TV-out on some pch-split platforms, so I've figured it doesn't
hurt to keep the code around a bit longer (e.g. in the cb tune
function).

v2: Improve the commit message as Jani suggested in his review.
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -5637,9 +5637,6 @@ static uint32_t ironlake_compute_dpll(struct intel_crtc *intel_crtc,
 			if (intel_encoder->needs_tv_clock)
 				is_tv = true;
 			break;
-		case INTEL_OUTPUT_TVOUT:
-			is_tv = true;
-			break;
 		}
 
 		num_connectors++;
@@ -5698,13 +5695,7 @@ static uint32_t ironlake_compute_dpll(struct intel_crtc *intel_crtc,
 		break;
 	}
 
-	if (is_sdvo && is_tv)
-		dpll |= PLL_REF_INPUT_TVCLKINBC;
-	else if (is_tv)
-		/* XXX: just matching BIOS for now */
-		/*	dpll |= PLL_REF_INPUT_TVCLKINBC; */
-		dpll |= 3;
-	else if (is_lvds && intel_panel_use_ssc(dev_priv) && num_connectors < 2)
+	if (is_lvds && intel_panel_use_ssc(dev_priv) && num_connectors < 2)
 		dpll |= PLLB_REF_INPUT_SPREADSPECTRUMIN;
 	else
 		dpll |= PLL_REF_INPUT_DREFCLK;