tg3: Add rx prod ring consolidation

This patch adds code to funnel each MSI-X vector's rx packet buffers
into a single set of producer rings which will then be submitted to the
hardware.

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