nfc: nci: remove unnecessary null check

Remove unnecessary NULL check for pointer conn_info.
conn_info is set in list_for_each_entry() using container_of(),
which is never NULL.

Addresses-Coverity-ID: 1362349
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>