drm/i915/fbc: Enable fbc on i865

Unlike all the other pre-snb desktop platforms i865 actually
supports FBC. Let's enable it.

Quote from the spec:
"DevSDG provides the same Run-Length Encoded Frame Buffer
 Compression (RLEFBC) function as exists in DevMGM."

As i865 only has the one pipe we want to skip massaging the
plane<->pipe assignment aimed at getting FBC+LVDS working on
the mobile platforms.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200702153723.24327-4-ville.syrjala@linux.intel.comReviewed-by: NJosé Roberto de Souza <jose.souza@intel.com>

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

@@ -16332,7 +16332,8 @@ intel_primary_plane_create(struct drm_i915_private *dev_priv, enum pipe pipe)
 	 * On gen2/3 only plane A can do FBC, but the panel fitter and LVDS
 	 * port is hooked to pipe B. Hence we want plane A feeding pipe B.
 	 */
-	if (HAS_FBC(dev_priv) && INTEL_GEN(dev_priv) < 4)
+	if (HAS_FBC(dev_priv) && INTEL_GEN(dev_priv) < 4 &&
+	    INTEL_NUM_PIPES(dev_priv) == 2)
 		plane->i9xx_plane = (enum i9xx_plane_id) !pipe;
 	else
 		plane->i9xx_plane = (enum i9xx_plane_id) pipe;

drivers/gpu/drm/i915/i915_pci.c

@@ -217,6 +217,7 @@ static const struct intel_device_info i85x_info = {
 static const struct intel_device_info i865g_info = {
 	I845_FEATURES,
 	PLATFORM(INTEL_I865G),
+	.display.has_fbc = 1,
 };
 
 #define GEN3_FEATURES \