usb gadget: USB_GADGET_VBUS_DRAW Kconfig option

usb gadget: USB_GADGET_VBUS_DRAW Kconfig option

Offer a "how much VBUS power to request" configuration option
for USB gadgets that aren't using board-specific customization
of their gadget or (composite) configuration drivers.

Also remove a couple pointless "depends on USB_GADGET" bits
from the Kconfig text; booleans inside an "if USB_GADGET" will
already have that dependency.

Based on a patch from Justin Clacherty.

Signed-off-by: David Brownell <[email protected]>
Cc: Justin Clacherty <[email protected]>
Tested-by: Robert Jarzmik <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>