NFC: Fix LLCP compilation warning

nfc_llcp_general_bytes is defined in nfc/core.c as:
nfc_llcp_general_bytes(struct nfc_dev *dev, size_t *gb_len).

as in nfc/nfc.h:
nfc_llcp_general_bytes(struct nfc_dev *dev, u8 *gb_len), if CONFIG_NFC_LLCP
is not defined.

so we got some warnings,
net/nfc/core.c:207:2: warning: passing argument 2 of ‘nfc_llcp_general_bytes’ from incompatible pointer type [enabled by default]
net/nfc/nfc.h:87:19: note: expected ‘u8 *’ but argument is of type ‘size_t *’

Signed-off-by: joseph daniel <josephdanielwalter@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>