bnx2: Fix reset bug on 5709

The 5709 chip requires the BNX2_MISC_NEW_CORE_CTL_DMA_ENABLE bit to be
cleared and polling for pending DMAs to complete before chip reset.
Without this step, we've seen NMIs during repeated resets of the chip.

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