ESP8285 uses incorrect 'generic' variant in board definition

[CapnBry]

Hello folks, I'm from the ExpressLRS project where we use quite a bit of ESP8285 chips in our various receivers.

I ran into a bit of a problem using GPIO9 and GPIO10 with the waveform generator and found that the esp8285.json selects the "generic" variant and not the "esp8285" variant present in the Arduino platform (present since 2018). The generic variant blocks the use of GPIO9/10 as being reserved for flash, but on the 8285 these two are free because the internal flash is only connected with two of the four SD GPIO.

The fix is just to change "generic" to "esp8285" in that json file.