NFC: port100: Convert cpu_to_le16(le16_to_cpu(E1) + E2) to use le16_add_cpu().

Convert cpu_to_le16(le16_to_cpu(frame->datalen) + len) to
use le16_add_cpu(), which is more concise and does the same thing.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/port100.c

@@ -565,7 +565,7 @@ static void port100_tx_update_payload_len(void *_frame, int len)
 {
 	struct port100_frame *frame = _frame;
 
-	frame->datalen = cpu_to_le16(le16_to_cpu(frame->datalen) + len);
+	le16_add_cpu(&frame->datalen, len);
 }
 
 static bool port100_rx_frame_is_valid(void *_frame)