usb: misc: Add driver for usb4604

This is a minimal driver to support bringing a usb4604 device
from microchip out of reset and into hub mode. The usb4604 device
is related to the usb3503 device, but it didn't seem close enough
to warrant putting both into the same file. This patch borrows
some of the usb3503 structure and trims it down to just handle
the optional reset gpio and adds the i2c command to put the
device into hub mode.

Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/00001716A.pdf


Cc: <devicetree@vger.kernel.org>
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>