Fix pin names of K64F with the following from the latest guidelines:
* LEDs and buttons are defined as macros, digital and analog pins as
enums.
* No duplicated pin names with the same value.
* The Arduino form factor is deprecated in favour of Arduino Uno.

Note: The pins `SPI_xxx` are for SD card only, but the names are kept
for backward compatibility (i.e. no breaking change until the next
Mbed OS major version). The general purpose Arduino Uno SPI pins
(`ARDUINO_UNO_SPI_xxx`) are different and also available.