drivers/ieee802154_kw41z: Reduce debug logging due to false positives

- Removed some debug output and changed the level of others to reduce
  the amount of information logged. The reason is that some of this is
  causing false positive distractions.
- Removed enabling of FILTER error IRQ events. It isn't needed and is
  only informational.
- Changed frame control AR bit inspection to use native retrieval
  routine.
- Addressed some coding style issues.

Signed-off-by: David Leach <david.leach@nxp.com>