Be more robust when handling Rx interrupts.  If we can't allocate and DMA map a new mbuf, just discard the received frame and reuse the old mbuf. This should fix kernel panics on high network traffic.
Be more robust when handling Rx interrupts.  If we can't allocate and DMA map
a new mbuf, just discard the received frame and reuse the old mbuf.
This should fix kernel panics on high network traffic.

Obtained from:  NetBSD (joerg@)
MFC after:      2 weeks

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