net: ftgmac100: Fix Aspeed ast2600 TX hang issue

net: ftgmac100: Fix Aspeed ast2600 TX hang issue

BugLink: https://bugs.launchpad.net/bugs/1902115
[ Upstream commit 137d23cea1c044b2d4853ac71bc68126b25fdbb2 ]

The new HW arbitration feature on Aspeed ast2600 will cause MAC TX to
hang when handling scatter-gather DMA.  Disable the problematic feature
by setting MAC register 0x58 bit28 and bit27.

Fixes: 39bfab8844a0 ("net: ftgmac100: Add support for DT phy-handle property")
Signed-off-by: Dylan Hung <dylan_hung@aspeedtech.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>