NFC: hci: delete unused nfc_llc_get_rx_head_tail_room()

It used to be EXPORTed, but then EXPORT usage was cleaned up
(in 2012), without noticing that the function has no users at all
(and curiously, never had any users).

Delete it.

While at it, remove non-static "inline" hints on nearby functions:
these hints don't work across compilation units anyway,
and these functions are not used in their .c file, thus they are
never inlined. IOW: "inline" here does not help in any way.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: Samuel Ortiz <sameo@linux.intel.com>
CC: Christophe Ricard <christophe.ricard@gmail.com>
CC: linux-wireless@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>