drm/i915: enable lvds pin pairs before dpll on gen2

Otherwise things migt not work too well.

Breakage introduced in

commit eb1cbe4
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Wed Mar 28 23:12:16 2012 +0200

    drm/i915: split PLL update code out of i9xx_crtc_mode_set

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@vger.kernel.org (for 3.5 only)
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -4191,19 +4191,19 @@ static void i8xx_update_pll(struct drm_crtc *crtc,
 	POSTING_READ(DPLL(pipe));
 	udelay(150);
 
-	I915_WRITE(DPLL(pipe), dpll);
-
-	/* Wait for the clocks to stabilize. */
-	POSTING_READ(DPLL(pipe));
-	udelay(150);
-
 	/* The LVDS pin pair needs to be on before the DPLLs are enabled.
 	 * This is an exception to the general rule that mode_set doesn't turn
 	 * things on.
 	 */
 	if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS))
 		intel_update_lvds(crtc, clock, adjusted_mode);
 
+	I915_WRITE(DPLL(pipe), dpll);
+
+	/* Wait for the clocks to stabilize. */
+	POSTING_READ(DPLL(pipe));
+	udelay(150);
+
 	/* The pixel multiplier can only be updated once the
 	 * DPLL is enabled and the clocks are stable.
 	 *