Remove the remnants of the workaround for erratum ERR005184 which was never
completely implemented.  The checks alone don't carry any value as we don't
act properly on the result.

A workaround should be added to the lane speed change in establish_link
later.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>