mppa: pktio: fix return value of early recv call
mppa: pktio: fix return value of early recv call

Recv requires the Tx side to be opened to work so it
 can send back credit to the CNoC mailbox.
If it is not the case, return 0 messages instead of an error

Signed-off-by: Nicolas Morey-Chaisemartin <7188b998d7bb37a035517aa285fa3f5a95344e80@kalray.eu>

kalray/odp-mppa,kalray/odp-mppa,kalray/odp-mppa,kalray/odp-mppa,kalray/odp-mppa,kalray/odp-mppa,kalray/odp-mppa