potential uninitialized variable num_xfrms

fix compiler warning: 'num_xfrms' may be used uninitialized in this function.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
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 net/xfrm/xfrm_policy.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Signed-off-by: David S. Miller <davem@davemloft.net>