net: use log_err() for 'No ethernet found' message

Write the 'No ethernet found' message via the log drivers. This allows
suppressing it during output via the syslog driver.

This fixes the problem reported in:

[PATCH 0/4] log: Fix the syslog spam when running tests
https://lists.denx.de/pipermail/u-boot/2020-September/426343.htmlReported-by: NSimon Glass <sjg@chromium.org>
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NSimon Glass <sjg@chromium.org>

net/eth-uclass.c

@@ -273,7 +273,7 @@ int eth_init(void)
 	if (!current) {
 		current = eth_get_dev();
 		if (!current) {
-			printf("No ethernet found.\n");
+			log_err("No ethernet found.\n");
 			return -ENODEV;
 		}
 	}
@@ -414,7 +414,7 @@ int eth_initialize(void)
 	 */
 	uclass_first_device_check(UCLASS_ETH, &dev);
 	if (!dev) {
-		printf("No ethernet found.\n");
+		log_err("No ethernet found.\n");
 		bootstage_error(BOOTSTAGE_ID_NET_ETH_START);
 	} else {
 		char *ethprime = env_get("ethprime");
@@ -449,7 +449,7 @@ int eth_initialize(void)
 		} while (dev);
 
 		if (!num_devices)
-			printf("No ethernet found.\n");
+			log_err("No ethernet found.\n");
 		putc('\n');
 	}
 

net/eth_legacy.c

@@ -261,7 +261,7 @@ int eth_initialize(void)
 	}
 
 	if (!eth_devices) {
-		puts("No ethernet found.\n");
+		log_err("No ethernet found.\n");
 		bootstage_error(BOOTSTAGE_ID_NET_ETH_START);
 	} else {
 		struct eth_device *dev = eth_devices;
@@ -319,7 +319,7 @@ int eth_init(void)
 	struct eth_device *old_current;
 
 	if (!eth_current) {
-		puts("No ethernet found.\n");
+		log_err("No ethernet found.\n");
 		return -ENODEV;
 	}