net: icmpv4: fix incorrect IP header checksum

IPv4 header's checksum was set when 'setup_ipv4_header', but in that
times IPv4 header's source ip and dest ip address haven't setted. So
it may be set an incorrect checksum.

Fixes: #7989

Signed-off-by: qianfan Zhao <qianfanguijin@163.com>