SX1276Random() breaks after a while

[lthiery]

After a while, it will start returning 0 or some power of 2. This is problematic, especially when it consistently returns 0's because the packet_id must be non-zero.

My hunch is that we need to enable antenna control properly to move forward. The Semtech library wants to enable the antenna for receive to get the random samples, but the code here has gutted most of the control efforts and most bindings implementation don't actually provide pin control for anything other than SPI CS.

What's odd to me is that it starts at non-zero and eventually becomes 0 after a long time, so its making me doubt the antenna explanation. In addition, when you sleep the chip for a few minutes and start talking to it again, proper random number start to show up.

Perhaps there is a finite amount of samples you can take from this register? Seems odd.