serial: fix port type conflict between NS16550A & U6_16550A

Bug seen by Dr. David Alan Gilbert with sparse

Signed-off-by: Philippe Langlais <philippe.langlais@stericsson.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/serial.h b/include/linux/serial.h
index 1ebc694..ef91406 100644
--- a/include/linux/serial.h
+++ b/include/linux/serial.h
@@ -77,8 +77,7 @@
 #define PORT_16654	11
 #define PORT_16850	12
 #define PORT_RSA	13	/* RSA-DV II/S card */
-#define PORT_U6_16550A	14
-#define PORT_MAX	14
+#define PORT_MAX	13
 
 #define SERIAL_IO_PORT	0
 #define SERIAL_IO_HUB6	1