net/faraday: fix grammar in function ftgmac100_setup_clk() in ftgmac100.c

"its not" is wrong. The words should be "it's not".
Signed-off-by: Hu Haowen <xianfengting221@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/faraday/ftgmac100.c

@@ -1731,7 +1731,7 @@ static int ftgmac100_setup_clk(struct ftgmac100 *priv)
 	if (rc)
 		goto cleanup_clk;
 
-	/* RCLK is for RMII, typically used for NCSI. Optional because its not
+	/* RCLK is for RMII, typically used for NCSI. Optional because it's not
 	 * necessary if it's the AST2400 MAC, or the MAC is configured for
 	 * RGMII, or the controller is not an ASPEED-based controller.
 	 */