usb: host: ehci-platform: Add workaround for brcm, xgs-iproc-ehci

The ehci controller found in some Broadcom switches with integrated SoCs
has an issue which causes a soft lockup with large transfers like you
see when running ext4 on USB3 flash drive.

Port the fix from the Broadcom XLDK to increase the OUT_THRESHOLD to
avoid the problem.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20200913215926.29880-1-chris.packham@alliedtelesis.co.nz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>