NFC: Set and get DEP general bytes

Without an API for setting and getting the local and remote general bytes,
drivers won't be able to properly establish a DEP link.
This API also allows them to propagate the remote general bytes they get
from the DEP link establishment up to the LLCP layer.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>