nimble/phy: Fix for late RX-TX transition on nRF52
nimble/phy: Fix for late RX-TX transition on nRF52

RX-TX transition on nRF52 is done by triggering TXEN using TIMER0 as we
do T_IFS in software. However, it may happen that timer set for TIMER0
is behind current TIMER0 counter and thus we will not start TX and thus
effectively block phy.

For now we will use a little hack: just indicate that we were late on
setting transition timer and this will make ble_phy_tx() fail so we can
recover easily. This seems much cleaner than hacking extra handling in
many other functions, so let's use such workaround for now.

X-Original-Commit: dd132d43d5facb8e538e1e2277f9a47bba4bdd40

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble