NFC: Fix LLCP related build failure

llcp_mac routines should be static and inlined or build will fail with NFC
selected without LLCP.

This patch fixes:

LD [M]  net/nfc/nfc.o
net/nfc/netlink.o: In function `nfc_llcp_mac_is_down':
netlink.c:(.text+0x0): multiple definition of `nfc_llcp_mac_is_down'
net/nfc/core.o:(.text+0x0): first defined here
net/nfc/netlink.o: In function `nfc_llcp_mac_is_up':
netlink.c:(.text+0x10): multiple definition of `nfc_llcp_mac_is_up'
net/nfc/core.o:(.text+0x10): first defined here
net/nfc/af_nfc.o: In function `nfc_llcp_mac_is_down':
(.text+0x0): multiple definition of `nfc_llcp_mac_is_down'
net/nfc/core.o:(.text+0x0): first defined here
net/nfc/af_nfc.o: In function `nfc_llcp_mac_is_up':
(.text+0x10): multiple definition of `nfc_llcp_mac_is_up'
net/nfc/core.o:(.text+0x10): first defined here
net/nfc/rawsock.o: In function `nfc_llcp_mac_is_down':
rawsock.c:(.text+0x0): multiple definition of `nfc_llcp_mac_is_down'
net/nfc/core.o:(.text+0x0): first defined here
net/nfc/rawsock.o: In function `nfc_llcp_mac_is_up':
rawsock.c:(.text+0x10): multiple definition of `nfc_llcp_mac_is_up'
net/nfc/core.o:(.text+0x10): first defined here

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