NFC: llcp: Use localy stored remote_miu value if not set at socket level

If remote_miu value is not set in the socket (i.e. connection-less socket) the
value stored in the local is used.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>