ipvs: Consistently use array_size() in ip_vs_conn_init()

Consistently use array_size() to calculate the size of ip_vs_conn_tab
in bytes.

Flagged by Coccinelle:
 WARNING: array_size is already used (line 1498) to compute the same size

No functional change intended.
Compile tested only.

Signed-off-by: Simon Horman <horms@kernel.org>
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>