tg3: Fix rx hang on MTU change with 5717/5719

tg3: Fix rx hang on MTU change with 5717/5719

This fixes a hang issue seen when changing the MTU size from 1500 MTU
to 9000 MTU on both 5717 and 5719 chips. In discussion with Broadcom,
they've indicated that these chipsets have the same phy as the 57766
chipset, so the same workarounds apply. This has been tested by IBM
on both Power 8 and Power 9 systems as well as by Broadcom on x86
hardware and has been confirmed to resolve the hang issue.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>