drm/i915: ELiminate intel_pipe_to_cpu_transcoder() from assert_fdi_tx()

Let's start to eliminate intel_pipe_to_cpu_transcoder() so that
we can get rid of one more crtc->config usage (which we will want
to nuke as well).

In the case of assert_fdi_tx() we know that we're never
dealing with the EDP transcoder so we can simply replace
this with a cast.

v2: Fix poor English in comment

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191112163812.22075-3-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>

drivers/gpu/drm/i915/display/intel_display.c

@@ -1146,11 +1146,15 @@ static void assert_fdi_tx(struct drm_i915_private *dev_priv,
 			  enum pipe pipe, bool state)
 {
 	bool cur_state;
-	enum transcoder cpu_transcoder = intel_pipe_to_cpu_transcoder(dev_priv,
-								      pipe);
 
 	if (HAS_DDI(dev_priv)) {
-		/* DDI does not have a specific FDI_TX register */
+		/*
+		 * DDI does not have a specific FDI_TX register.
+		 *
+		 * FDI is never fed from EDP transcoder
+		 * so pipe->transcoder cast is fine here.
+		 */
+		enum transcoder cpu_transcoder = (enum transcoder)pipe;
 		u32 val = I915_READ(TRANS_DDI_FUNC_CTL(cpu_transcoder));
 		cur_state = !!(val & TRANS_DDI_FUNC_ENABLE);
 	} else {