NETMAP: Some fixes

1) Correct the NIOCRXSYNC macro on receive side from NIOCTXSYNC.
2) Flush the pending messages in the tx rings.

Change-Id: I581040d03b1633a3d6fb22fa1fb285bcb7975afb
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
3 files changed