packet: use vzalloc()

alloc_one_pg_vec_page() is supposed to return zeroed memory, so use
vzalloc() instead of vmalloc()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>