NFC: nci: Use __nci_request for exported routines

Since we do not know in which context drivers will call these
routines, they should use the unlocked version of nci_request,
i.e. __nci_request.
It is up to drivers to know/decide if they need to take the
req_lock mutex before calling those routines. When being called
from the NCI setup routine there is no need to do so as ops->setup
is called under req_lock.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>