[][kernel][common][app][Fix coverity issue for the switch utility]

[Description]
Fix coverity issue for the switch utility.

Without this patch, the coverity might detect UNUSED_VALUE warning in
the mii_mgr_cl45_read_indirect() and mii_mgr_cl45_write_indirect().

[Release-log]
N/A


Change-Id: If3428b07a02170e2cfd1529d585b61ca9a50803b
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7947206
diff --git a/feed/switch/src/switch_ioctl.c b/feed/switch/src/switch_ioctl.c
index f6b97d4..366079e 100644
--- a/feed/switch/src/switch_ioctl.c
+++ b/feed/switch/src/switch_ioctl.c
@@ -235,18 +235,24 @@
 	mii.reg_num = 13;
 	mii.val_in = dev;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	method = RAETH_MII_WRITE;
 	mii.phy_id = port_num;
 	mii.reg_num = 14;
 	mii.val_in = reg;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	method = RAETH_MII_WRITE;
 	mii.phy_id = port_num;
 	mii.reg_num = 13;
 	mii.val_in = (0x6000 | dev);
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	usleep(1000);
 
@@ -254,6 +260,8 @@
 	mii.phy_id = port_num;
 	mii.reg_num = 14;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	close(sk);
 	*value = mii.val_out;
@@ -283,18 +291,24 @@
 	mii.reg_num = 13;
 	mii.val_in = dev;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	method = RAETH_MII_WRITE;
 	mii.phy_id = port_num;
 	mii.reg_num = 14;
 	mii.val_in = reg;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	method = RAETH_MII_WRITE;
 	mii.phy_id = port_num;
 	mii.reg_num = 13;
 	mii.val_in = (0x6000 | dev);
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	usleep(1000);
 
@@ -303,6 +317,8 @@
 	mii.reg_num = 14;
 	mii.val_in = value;
 	ret = ioctl(sk, method, &ifr);
+	if (ret < 0)
+		printf("ioctl failed with error %d\n", ret);
 
 	close(sk);