Declaration of lmic_hal_set_failure_handler is demented

[terrillmoore]

It's not actually incorrect, but it has a lot more consts than are needed.

It is:

arduino-lmic/src/lmic/hal.h

Line 147 in d343853

void lmic_hal_set_failure_handler(const lmic_hal_failure_handler_t* const);

It should be:

void lmic_hal_set_failure_handler (lmic_hal_failure_handler_t*);