tty: n_tty: use min3() in copy_from_read_buf()

n is a minimum of:
* available chars in the ring buffer
* available chars in the ring buffer till the end of the ring buffer
* requested number (*nr)

We can use min3() for that instead of two min()s.
Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230919085156.1578-4-jirislaby@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -1965,8 +1965,7 @@ static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
 	size_t head = smp_load_acquire(&ldata->commit_head);
 	size_t tail = MASK(ldata->read_tail);
 
-	n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
-	n = min(*nr, n);
+	n = min3(head - ldata->read_tail, N_TTY_BUF_SIZE - tail, *nr);
 	if (n) {
 		u8 *from = read_buf_addr(ldata, tail);
 		memcpy(*kbp, from, n);