nfc: hci: Save a few bytes of memory when registering a 'nfc_llc' engine

nfc_llc_register() calls pass a string literal as the 'name' parameter.

So kstrdup_const() can be used instead of kfree() to avoid a memory
allocation in such cases.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>