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` through `led_pin_6` as leds (in hopes of getting the pwm driver
   integrated here) named `pwm0` -> `pwm5`