mpipe: fix crash when testpmd is quit under load
mpipe: fix crash when testpmd is quit under load

Fixes: the hung/crash issue when quitting testpmd under high
traffic rate. The following issue were found and fixed.
1. edesc->size is not initialized properly in mpipe_do_xmit() and could
   cause buffer leak or corruption when HW buffer return is used.
2. Check the 'idesc.be' error bit in mpipe_recv_flush() to make sure
   buffer is valid before releasing it. This is to avoid issues when
   running out of buffers.
3. priv->rx_buffers counter is not accurate when HW buffer return is
   used. Remove this counter to simplify the code.

Signed-off-by: Liming Sun <aae9fae19e69d1c9dbe65b570b35150d89734aae@ezchip.com>
Acked-by: Zhigang Lu <d473c8ac947e53ca706b2148c5db2c971399f855@ezchip.com>

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