tty: n_tty: use 'retval' instead of 'c'

In n_tty_read(), there is a separate int variable 'c' and is used only
to hold an int value returned from job_control(). There is also a
'retval' variable typed ssize_t. So drop this single occurrence of 'c'
and reuse 'retval' which is used on all other places to hold the value
returned from n_tty_read().

Note that 'retval' needs not be initialized now. Drop that.
Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-2-jirislaby@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -2154,9 +2154,8 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 	struct n_tty_data *ldata = tty->disc_data;
 	u8 *kb = kbuf;
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
-	int c;
 	int minimum, time;
-	ssize_t retval = 0;
+	ssize_t retval;
 	long timeout;
 	bool packet;
 	size_t old_tail;
@@ -2192,9 +2191,9 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 		return kb - kbuf;
 	}
 
-	c = job_control(tty, file);
-	if (c < 0)
-		return c;
+	retval = job_control(tty, file);
+	if (retval < 0)
+		return retval;
 
 	/*
 	 *	Internal serialization of reads.