nimble/ll: Fix sending features xchange PDUs
nimble/ll: Fix sending features xchange PDUs

We only set single octet of CtrData field so need to clear other octets
as otherwise we can send some random value there.

X-Original-Commit: baa74ed2d3f6a5936b59c599265d2cd0296a6d69

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