[IPSEC]: Remove redundant check in xfrm_state_add()

[IPSEC]: Remove redundant check in xfrm_state_add()

This is the patch referred to in the netlink_get_spi thread.

I was actually wrong about the reason for this patch though.  Firstly
it's the SPI check that is redundant and not the find_acq() call.
And it's redundant because of the find_acq() patch, not because
of the fact that this is in xfrm_state_add().

Now that find_acq() only returns SAs with SPIs, we don't need to
check this in xfrm_state_add() anymore.

We do still need the call though to clean up leftover larval states.

Another side-effect of the change is that we can move the existence
check above find_acq() since find_acq() will never return any SAs
matching the SPI we're trying to add (It doesn't need to because if
an SA with a matching SPI existed, it would've been returned by
state_lookup() already).

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@redhat.com>