drm/nouveau/kms/tu102-: disable input lut when input is already FP16

On Turing, an input LUT is required to transform inputs in fixed-point
formats to FP16 for the internal display pipe.  We provide an identity
mapping whenever a window is enabled for this reason.

HW has error checks to ensure when the input is already FP16, that the
input LUT is also disabled.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/dispnv50/wndw.c

@@ -322,7 +322,9 @@ nv50_wndw_atomic_check_lut(struct nv50_wndw *wndw,
 		asyh->wndw.olut &= ~BIT(wndw->id);
 	}
 
-	if (!ilut && wndw->func->ilut_identity) {
+	if (!ilut && wndw->func->ilut_identity &&
+	    asyw->state.fb->format->format != DRM_FORMAT_XBGR16161616F &&
+	    asyw->state.fb->format->format != DRM_FORMAT_ABGR16161616F) {
 		static struct drm_property_blob dummy = {};
 		ilut = &dummy;
 	}