BugLink: http://bugs.launchpad.net/bugs/1693673

Prefetch buffer cleanup code was called twice, causing EDAC to
report errors during reboot.

[ 1130.972475] xgene-edac 78800000.edac: IOB bridge agent (BA) transaction
error
[ 1130.979584] xgene-edac 78800000.edac: IOB BA write response error
[ 1130.985648] xgene-edac 78800000.edac: IOB BA write access at 0x00.00000000
()
[ 1130.993612] xgene-edac 78800000.edac: IOB BA requestor ID 0x00002400
[ 1131.000242] xgene-edac 78800000.edac: IOB bridge agent (BA) transaction
error
...

This patch fixes the errors by,

- removing the redundant prefetch buffer cleanup from port_ops->shutdown()
- moving port_ops->shutdown() after delete_rings()
Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(back ported from commit 8aba8474)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>