drm/i915: drop buggy write to FDI_RX_CHICKEN register

Jani Nikula noticed that the parentheses are wrong and we & the bit
with the register address instead of the read-back value. He sent a
patch to correct that.

On second look, we write the same register in the previous line, and
the w/a seems to be to set FDI_RX_PHASE_SYNC_POINTER_OVR to enable the
logic, then keep always set FDI_RX_PHASE_SYNC_POINTER_OVR and toggle
FDI_RX_PHASE_SYNC_POINTER_EN before/after enabling the pc transcoder.

So the right things seems to be to simply kill the 2nd write.

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Dropped a bogus ~ from the commit message that somehow crept
in.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -2924,9 +2924,6 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
 	/* Ironlake workaround, disable clock pointer after downing FDI */
 	if (HAS_PCH_IBX(dev)) {
 		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
-		I915_WRITE(FDI_RX_CHICKEN(pipe),
-			   I915_READ(FDI_RX_CHICKEN(pipe) &
-				     ~FDI_RX_PHASE_SYNC_POINTER_EN));
 	} else if (HAS_PCH_CPT(dev)) {
 		cpt_phase_pointer_disable(dev, pipe);
 	}