serial: Remove unused port type

PORT_MFD is not in use since commit

	1bd187de ("x86, intel-mid: remove Intel MID specific serial support")

Remove leftover.

Fixes: 1bd187de ("x86, intel-mid: remove Intel MID specific serial support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/uapi/linux/serial_core.h

@@ -209,9 +209,6 @@
 /* MAX310X */
 #define PORT_MAX310X	94
 
-/* High Speed UART for Medfield */
-#define PORT_MFD	95
-
 /* TI OMAP-UART */
 #define PORT_OMAP	96