Nimble contains a couple of casts that discard alignment information.
This causes a warning with clang's -Wno-address-of-packed-member.
A previous PR (#10503) supressed that warning. This commit re-enables
them and provides a patch to fix the offending code.
The fix has been submitted upstream, see
https://github.com/apache/mynewt-nimble/pull/252
When building `nimble` with LLVM/clang the function
`ble_ll_adv_active_chanset_is_sec()` in `ble_ll_adv.c` is reported to
be unused, it is used within an assertions and `ifdef`s within that
file though. So this just disables that warning.
