net: stmmac: Restrict warning on disabling DMA store and fwd mode

When setting 'snps,force_thresh_dma_mode' DT property, the following
warning is always emitted, regardless the status of force_sf_dma_mode:

dwmac-starfive 10020000.ethernet: force_sf_dma_mode is ignored if force_thresh_dma_mode is set.

Do not print the rather misleading message when DMA store and forward
mode is already disabled.

Fixes: e2a240c ("driver:net:stmmac: Disable DMA store and forward mode if platform data force_thresh_dma_mode is set.")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20230210202126.877548-1-cristian.ciocaltea@collabora.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

@@ -559,7 +559,7 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
 	dma_cfg->mixed_burst = of_property_read_bool(np, "snps,mixed-burst");
 
 	plat->force_thresh_dma_mode = of_property_read_bool(np, "snps,force_thresh_dma_mode");
-	if (plat->force_thresh_dma_mode) {
+	if (plat->force_thresh_dma_mode && plat->force_sf_dma_mode) {
 		plat->force_sf_dma_mode = 0;
 		dev_warn(&pdev->dev,
 			 "force_sf_dma_mode is ignored if force_thresh_dma_mode is set.\n");