tty: can327, move overflow test inside can327_ldisc_rx()'s loop

The 'count' is going to be unsigned and the 'count >= 0' test would be
always true then. Move the condition to the loop where this is easier to
check.

It looks as is easier to follow after all too.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Max Staudt <[email protected]>
Cc: Wolfgang Grandegger <[email protected]>
Cc: Marc Kleine-Budde <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Jiri Slaby (SUSE)

drivers/net/can/can327.c

@@ -901,7 +901,13 @@ static void can327_ldisc_rx(struct tty_struct *tty, const unsigned char *cp,
 	 */
 	first_new_char_idx = elm->rxfill;
 
-	while (count-- && elm->rxfill < CAN327_SIZE_RXBUF) {
+	while (count--) {
+		if (elm->rxfill >= CAN327_SIZE_RXBUF) {
+			netdev_err(elm->dev,
+				   "Receive buffer overflowed. Bad chip or wiring? count = %i",
+				   count);
+			goto uart_failure;
+		}
 		if (fp && *fp++) {
 			netdev_err(elm->dev,
 				   "Error in received character stream. Check your wiring.");
@@ -930,13 +936,6 @@ static void can327_ldisc_rx(struct tty_struct *tty, const unsigned char *cp,
 		cp++;
 	}
 
-	if (count >= 0) {
-		netdev_err(elm->dev,
-			   "Receive buffer overflowed. Bad chip or wiring? count = %i",
-			   count);
-		goto uart_failure;
-	}
-
 	can327_parse_rxbuf(elm, first_new_char_idx);
 	spin_unlock_bh(&elm->lock);