usb: musb: davinci: Convert to use GPIO descriptor

usb: musb: davinci: Convert to use GPIO descriptor

The DaVinci MUSB glue contains an optional GPIO line to
control VBUS power, convert this to use a GPIO descriptor
and augment the EVM board file to provide this descriptor.

I can't get this driver to compile properly and it depends
on broken but when I didn get it to compile brokenly, it
did at least not complain about THIS code being broken so
I don't think I broke the driver any more than what it
already is.

I did away with the ifdefs that do not work with
multiplatform anyway so the day someone decides to
resurrect the code, the path to get it working should be
easier as well since DaVinci is now multiplatform.

Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[b-liu@ti.com: fixed one instance still ref to global variable vbus_state]
Signed-off-by: Bin Liu <b-liu@ti.com>
Link: https://lore.kernel.org/r/20200115132547.364-25-b-liu@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>