vxge: Fix a receive stall due to driver being out of synch with chip.

- Fix a receive stall due to driver being out of synch with chip. In a corner
case scenario the adapter's ring controller may return a RxD with transfer code
of 0xC, while the host ownership bit is still set to the adapter. The driver
needs to assume that this case where (host_ownership == 1 or adapter) and
(transfer_code == 0xC) is valid, that is, this RxD has been returned by the
receive ring controller but no frame data is associated with the rxd.

- Restore the transfer code field of each newly replenished RxD to 0x0.

- Code cleanup. Removed usage of magic numbers.

Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@neterion.com>
Signed-off-by: Ramkrishna Vepa <ram.vepa@neterion.com>
Signed-off-by: David S. Miller <davem@davemloft.net>