Add LMIC_setClockError() after LMIC_reset(); for 32u4 Lora

[samlist21]

LMIC_reset();

// Set after reset becasue of this link:
LMIC_setClockError(MAX_CLOCK_ERROR * 5 / 100);

This information comes from: https://www.thethingsnetwork.org/forum/t/ev-join-failed-with-adafruit-feather-32u4-and-lmic/7252/2

This code may be necessary to get the a 32u4 working. 1 unit didn't need it but my other two units did. Once they had this code entered they joined in the first transmission. Suggest an ifdef statement and a Define 32u4 in the project config file.