Bluetooth: Create a unique mgmt error code hierarchy

The management protocol uses a single byte for error codes (aka command
status). In some places this value is directly copied from HCI and in
other a POSIX error number is used. This makes it impossible for
user-space to uniquily decipher the meaning of an error.

To solve this issue a new mgmt-specific set of error codes is added
along with a conversion table for HCI status values.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>