Revert "tty:revert the tty update from qcom for moto tty_diag driver"

Keep the upstream pty driver
Adjust the moto tty_diag to solve the watchdog panic

This reverts commit 257cf44a1f9264ced64fde12868ed543a7d270af.

Change-Id: Id362323694562ba26f5531099ce32da649872476
Signed-off-by: a17671 <a17671@motorola.com>
Reviewed-on: https://gerrit.mot.com/2130818
SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>
Submit-Approved: Jira Key

drivers/tty/pty.c

@@ -120,10 +120,10 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 		spin_lock_irqsave(&to->port->lock, flags);
 		/* Stuff the data into the input queue of the other end */
 		c = tty_insert_flip_string(to->port, buf, c);
+		spin_unlock_irqrestore(&to->port->lock, flags);
 		/* And shovel */
 		if (c)
 			tty_flip_buffer_push(to->port);
-		spin_unlock_irqrestore(&to->port->lock, flags);
 	}
 	return c;
 }