PCI: rcar: Use correct initial HW settings

Although the R-Car PCIe driver works as it is, there are a number of
incorrect settings that this patch corrects. It corrects:
 - enabling the PCI Express Extended Cap ID.
 - setting Data Link Layer Link Active Reporting Capable.
 - terminating list of capabilities.

It also removes enabling the MAC data scrambling as this is the default HW
setting, and removes incorrect code to enable slave bus mastering as this
is done by the PCI core.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>