n_tty: move echoctl check and clean up logic

diff -Nurp b/drivers/char/n_tty.c c/drivers/char/n_tty.c
@@ -577,33 +577,23 @@ static void process_echoes(struct tty_st
 				break;
 
 			default:
-				if (iscntrl(op)) {
-					if (L_ECHOCTL(tty)) {
-						/*
-						 * Ensure there is enough space
-						 * for the whole ctrl pair.
-						 */
-						if (space < 2) {
-							no_space_left = 1;
-							break;
-						}
-						tty_put_char(tty, '^');
-						tty_put_char(tty, op ^ 0100);
-						tty->column += 2;
-						space -= 2;
-					} else {
-						if (!space) {
-							no_space_left = 1;
-							break;
-						}
-						tty_put_char(tty, op);
-						space--;
-					}
-				}
 				/*
-				 * If above falls through, this was an
-				 * undefined op.
+				 * If the op is not a special byte code,
+				 * it is a ctrl char tagged to be echoed
+				 * as "^X" (where X is the letter
+				 * representing the control char).
+				 * Note that we must ensure there is
+				 * enough space for the whole ctrl pair.
+				 *
 				 */
+				if (space < 2) {
+					no_space_left = 1;
+					break;
+				}
+				tty_put_char(tty, '^');
+				tty_put_char(tty, op ^ 0100);
+				tty->column += 2;
+				space -= 2;
 				cp += 2;
 				nr -= 2;
 			}

@@ -810,8 +800,8 @@ static void echo_char_raw(unsigned char 
  *	Echo user input back onto the screen. This must be called only when
  *	L_ECHO(tty) is true. Called from the driver receive_buf path.
  *
- *	This variant tags control characters to be possibly echoed as
- *	as "^X" (where X is the letter representing the control char).
+ *	This variant tags control characters to be echoed as "^X"
+ *	(where X is the letter representing the control char).
  *
  *	Locking: echo_lock to protect the echo buffer
  */

@@ -824,7 +814,7 @@ static void echo_char(unsigned char c, s
 		add_echo_byte(ECHO_OP_START, tty);
 		add_echo_byte(ECHO_OP_START, tty);
 	} else {
-		if (iscntrl(c) && c != '\t')
+		if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
 			add_echo_byte(ECHO_OP_START, tty);
 		add_echo_byte(c, tty);
 	}