drm/i915: check eDP encoder correctly when setting modes

We were using a stale pointer in the check which caused us to use CPU
attached DP params when we should have been using PCH attached params.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31988
Tested-by: Jan-Hendrik Zab <jan@jhz.name>
Tested-by: Christoph Lukas <christoph.lukas@gmx.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

drivers/gpu/drm/i915/intel_display.c

@@ -3951,7 +3951,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		int lane = 0, link_bw, bpp;
 		/* CPU eDP doesn't require FDI link, so just set DP M/N
 		   according to current link config */
-		if (has_edp_encoder && !intel_encoder_is_pch_edp(&encoder->base)) {
+		if (has_edp_encoder && !intel_encoder_is_pch_edp(&has_edp_encoder->base)) {
 			target_clock = mode->clock;
 			intel_edp_link_config(has_edp_encoder,
 					      &lane, &link_bw);