netfilter:ipvs: use kmemdup

The semantic patch that makes this output is available
in scripts/coccinelle/api/memdup.cocci.

More information about semantic patching is available at
http://coccinelle.lip6.fr/



Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: Simon Horman <horms@verge.net.au>