catena4612_simple in US915 loses channel mask on reset

[terrillmoore]

With the current (master) version of LMIC, a reset causes a Catena to start transmitting on all channels, rather than on the TTN US subset. Probably we need to fix the LMIC, as this is an annoying compatibility issue. This is clearly due to a change in how LMIC_reset() initializes things interacting with when we select the subband and then reload the saved paramters. Could be an arduino-lorawan problem.