[TG3]: Fix tg3_get_ringparam()

Fix-up tg3_get_ringparam() to return the correct parameters.

Set the jumbo rx ring parameter only if it is supported by the chip
and currently in use.

Add missing value for tx_max_pending, noticed by Rick Jones.

Update version to 3.51.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>