PCI: cadence: Retrain Link to work around Gen2 training defect

PCI: cadence: Retrain Link to work around Gen2 training defect

[ Upstream commit 4740b969aaf58adeca6829947a3ad8da423976cf ]

Cadence controller will not initiate autonomous speed change if strapped
as Gen2. The Retrain Link bit is set as quirk to enable this speed change.

Link: https://lore.kernel.org/r/20210209144622.26683-3-nadeem@cadence.com
Signed-off-by: Nadeem Athani <nadeem@cadence.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>