net: macb: remove BUG_ON() and reset the queue to handle RX errors

This patch removes two BUG_ON() used to notify about RX queue corruptions
on macb (not gem) hardware without actually handling the error.

The new code skips corrupted frames but still processes faultless frames.
Then it resets the RX queue before restarting the reception from a clean
state.

This patch is a rework of an older patch proposed by Neil Armstrong:
http://patchwork.ozlabs.org/patch/371525/

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>