[XFRM]: Remove unused exports.

This patch removes the following no longer used EXPORT_SYMBOL's:
- xfrm_input.c: xfrm_parse_spi
- xfrm_state.c: xfrm_replay_check
- xfrm_state.c: xfrm_replay_advance

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>