* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro
Squashed commit of the following:
wireless/bluetooth: Some small changes that gets to a clean compile by just eliminating some incorrect implementations (still with a lot of warnings. The logic is still incomplete but now not so lethal.
wireless/bluetooth: Restructuring: Connection interfaces should internal to wireless/bluetooth. include/nuttx/wireless/bt_conn.h removed and merged with wireless/bluetooth/bt_conn.h. Several fix to get closer to bt_netdev.c compiling. Need to design some not interfaces and use some existing interfaces to send and receiv packets.
wireless/bluetooth: Some organization with some network device compile errors fixed. Still not even close to compiling.
net/bluetooth: Fix numerous compile issues; Still open design issues with regard to the interface with the Bluetooth stack.
wireless/bluetooth: Create bt_netdev.c with a crude copy of mac802154_netdev.c. Does not not even compile yet.
include/nuttx/net: Add bluetooth.h. Content is not yet correct.
net/netpackets: Add bluetooth.h. Update net/bluetooth to use new socket address definition.
net/bluetooth: Some fixes for initial build.
net/bluetooth: Add initial support for Bluetooth sockets. The initial cut is just the a clone of the IEEE 802.15.4 socket support with name changes.
net/ieee802154: Fix some typos noted when cloning to create net/bluetooth.
