Bluetooth: btuart_cs: Comparison to NULL re-written

NOT NULL comparison modified to be readable, reported
by checkpatch.

Signed-off-by: Prasanna Karthik <mkarthi3@visteon.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/bluetooth/btuart_cs.c b/drivers/bluetooth/btuart_cs.c
index abb4d21..dfaa1c9 100644
--- a/drivers/bluetooth/btuart_cs.c
+++ b/drivers/bluetooth/btuart_cs.c
@@ -188,7 +188,7 @@
 		info->hdev->stat.byte_rx++;
 
 		/* Allocate packet */
-		if (info->rx_skb == NULL) {
+		if (!info->rx_skb) {
 			info->rx_state = RECV_WAIT_PACKET_TYPE;
 			info->rx_count = 0;
 			info->rx_skb = bt_skb_alloc(HCI_MAX_FRAME_SIZE, GFP_ATOMIC);