New driver for CP2130 USB-to-SPI bridge

[Jochen Henneberg <jh@xxxxxxxxxxxxxxxxxxxxxxxxxx>]

This is a new driver to support the Silicon Labs CP2130 USB-to-SPI
bridge. There are some warning left from checkpatch.pl but I would
consider those as false negatives as they will reduce code
readability.

The check script also suggests to edit the maintainers list. If this
helps I would be willing to provide maintenance for the driver. Just
let me know.

The driver has been used by several people as you can see from the
Github repository https://github.com/Henneberg-Systemdesign/cp2130[1][1].

I am using the driver with the MCP215x CAN controller, the Holt
HI-3593 transceiver and some Analog Devices DSPs.