arm: a37xx: pci: Set Max Payload Size and Max Read Request Size to 512 bytes

arm: a37xx: pci: Set Max Payload Size and Max Read Request Size to 512 bytes

Fix usage of VL805 XHCI PCIe controller when it is connected via PCIe to
Armada 3720 SOC. Without this U-Boot crashes when trying to access
enumerated USB devices connected to this XHCI PCIe controller.

This should be done according to the PCIe Link Initialization sequence, as
defined in Marvell Armada 3720 Functional Specification.

Linux has this code too.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>