esp32_lora: build errors

[c64emulator]

I had two compile and link errors during build, this is how I resolved:

1. 'LMIC_UNUSED_PIN' was not declared in this scope: add include for u1_t type in file src/hal/hal.h, after line 15 (see commit at [https://github.com/mcci-catena/arduino-lmic/commit/5bcd2469d3d2c1fae5659a3de249cb31e9121891]):

   #include "lmic/oslmic_types.h"

2. multiple definition of hal_init: adding -D hal_init=LMICHAL_init to the build_flags in the platformio.ini file (see issue #41 at [https://github.com/lnlp/LMIC-node/issues/41#issuecomment-1112346011])