net/mvpp2: update Tx checksum
net/mvpp2: update Tx checksum

According to the dpdk spec, only 'ol_flags'
should be used for tx checksum generation

Signed-off-by: Liron Himi <df7a1fcdffe73785b04dbbbb050c783d856d9736@marvell.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk