usb: isp1760: use relaxed primitives

Use io relaxed access memory primitives to satisfy strict type
checking (__force).

This will fix some existing sparse warnings:
sparse: warning: cast to restricted __le32

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210513084717.2487366-4-rui.silva@linaro.org


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