Allow non-integer LoRa Frequencies

[nesanakin]

On the ground unit, the 'freq' setting should allow for non-integer frequencies for the LoRa radio. Due to the flooring division on line 392 of main.py:

Loko/Software/LokoGround Firmware/main_1.1.py

Line 392 in 5ae61c4

freq_mhz = freq_hz // 1000000

Frequencies are rounded to integer MHz values. For example, I am using 919875000 Hz, which is incorrectly rounded to 919000000 Hz. A simple change to use regular division:

    freq_mhz = freq_hz / 1000000

Corrects the issue.

Thanks!