mbuf: add functions to dump offload flags

mbuf: add functions to dump offload flags

The functions rte_get_rx_ol_flag_name() and rte_get_tx_ol_flag_name()
can dump one flag, or set of flag that are part of the same mask (ex:
PKT_TX_UDP_CKSUM, part of PKT_TX_L4_MASK). But they are not designed to
dump the list of flags contained in mbuf->ol_flags.

This commit introduce new functions to do that. Similarly to the packet
type dump functions, the goal is to factorize the code that could be
used in several applications and reduce the risk of desynchronization
between the flags and the dump functions.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>