If the receiver runs out of space for an received frame in the internal

If the receiver runs out of space for an received frame in the internal
FIFO or the in-RAM descriptors it will switch to RX_IDLE from where it
is not restarted.

We used to deal with RX_IDLE by doing a total reinit but this lost
our link and caused a potential 30sec autonegotiation against
switches.  This was changed to a less heavyhanded approach, but this
failed to restart the receiver it it were in the RX_IDLE state.

This change adds the RX_IDLE and the RX_FIFO_OFLOW conditions as
triggers for interrupts and receive side processing, and restarts
the receiver when it is RX_IDLE.

Remove the #ifdef notyet'ed nge_rxeoc() function.

Sponsored by:	Cybercity Internet, Denmark.
MFC after:	7 days