tty/serial: atmel: increase ATMEL_MAX_UART

The samx7 family uses the same UART/USART IP as the at91/sama5 families but
has 8 of those.
Suggested-by: Szemző András <sza@esh.hu>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -119,8 +119,9 @@ struct atmel_uart_char {
 /*
  * at91: 6 USARTs and one DBGU port (SAM9260)
  * avr32: 4
+ * samx7: 3 USARTs and 5 UARTs
  */
-#define ATMEL_MAX_UART		7
+#define ATMEL_MAX_UART		8
 
 /*
  * We wrap our port structure around the generic uart_port.