NFC: Include nci_core.h to nci/lib.c

Include the header to pickup the exported symbol prototype.

Quites the sparse warning:

warning: symbol 'nci_to_errno' was not declared. Should it be static?

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
Cc: Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
CC: Samuel Ortiz <sameo@linux.intel.com>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>