commit 9bc297ea upstream.

Commit 091f0ea3 "tg3: Add New 5719 Read
DMA workaround" added a workaround for TX DMA stall on the 5719. This
workaround needs to be applied to the 5720 as well.
Reported-by: Roland Dreier <roland@purestorage.com>
Tested-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: use GET_ASIC_REV() instead of tg3_asic_rev()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[hq: Backproted to 3.4: Adjust context]
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>