Tweak serial port descriptions

Marlin/Configuration.h

@@ -99,6 +99,7 @@
 /**
  * Select the serial port on the board to use for communication with the host.
  * This allows the connection of wireless adapters (for instance) to non-default port pins.
+ * Serial port -1 is the USB emulated serial port, if available.
  * Note: The first serial port (-1 or 0) will always be used by the Arduino bootloader.
  *
  * :[-1, 0, 1, 2, 3, 4, 5, 6, 7]
@@ -107,9 +108,6 @@
 
 /**
  * Select a secondary serial port on the board to use for communication with the host.
- * This allows the connection of wireless adapters (for instance) to non-default port pins.
- * Serial port -1 is the USB emulated serial port, if available.
- *
  * :[-1, 0, 1, 2, 3, 4, 5, 6, 7]
  */
 //#define SERIAL_PORT_2 -1