[NET]: uninline dst_release

Codiff stats (allyesconfig, v2.6.24-mm1):
-16420  187 funcs, 103 +, 16523 -, diff: -16420 --- dst_release

Without number of debug related CONFIGs (v2.6.25-rc2-mm1):
-7257  186 funcs, 70 +, 7327 -, diff: -7257 --- dst_release
dst_release                   |  +40

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>