Cleaned up the pin configuration a bit

 * in [gpio_para] 20 pins were declared, but the FEX format doesn't
   recognize `gpio_pin_0` and was complaining that it couldn't find
   gpio_pin_20 (_19 was the highest number).  Redeclared `gpio_pin_0` as `gpio_pin_20`
 * Added a [leds_para] section
 * declared PH15 as led_pin_7 named `green:ph15:txled` and PH16 as led_pin_8
   nameed `"green:ph16:txled"`
 * declared led_pin_1 -> led_pin_6 as leds (in hopes of getting the pwm driver
   integrated here) named `pwm0` -> `pwm5`