cmd: sf: Fix sf probe crash

Handle the return value of spi_flash_probe_bus_cs() to avoid sf probe
crashes.

Link: https://lore.kernel.org/all/20240104114619.280513-1-o451686892@gmail.com
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
diff --git a/cmd/sf.c b/cmd/sf.c
index 730996c..e386689 100644
--- a/cmd/sf.c
+++ b/cmd/sf.c
@@ -135,8 +135,9 @@
 	}
 	flash = NULL;
 	if (use_dt) {
-		spi_flash_probe_bus_cs(bus, cs, &new);
-		flash = dev_get_uclass_priv(new);
+		ret = spi_flash_probe_bus_cs(bus, cs, &new);
+		if (!ret)
+			flash = dev_get_uclass_priv(new);
 	} else {
 		flash = spi_flash_probe(bus, cs, speed, mode);
 	}