net: lan743x_ptp: make function lan743x_ptp_set_sync_ts_insert() static

Fixes the following sparse warning:

drivers/net/ethernet/microchip/lan743x_ptp.c:980:6: warning:
 symbol 'lan743x_ptp_set_sync_ts_insert' was not declared. Should it be static?
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/lan743x_ptp.c

@@ -977,7 +977,7 @@ void lan743x_ptp_close(struct lan743x_adapter *adapter)
 	lan743x_ptp_disable(adapter);
 }
 
-void lan743x_ptp_set_sync_ts_insert(struct lan743x_adapter *adapter,
+static void lan743x_ptp_set_sync_ts_insert(struct lan743x_adapter *adapter,
 					   bool ts_insert_enable)
 {
 	u32 ptp_tx_mod = lan743x_csr_read(adapter, PTP_TX_MOD);