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 <dbrownell@users.sourceforge.net>
Cc: Justin Clacherty <justin@redfish-group.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/gmidi.c b/drivers/usb/gadget/gmidi.c
index 6eee760..60d3f9e 100644
--- a/drivers/usb/gadget/gmidi.c
+++ b/drivers/usb/gadget/gmidi.c
@@ -222,7 +222,7 @@
 	 * power properties of the device. Is it selfpowered?
 	 */
 	.bmAttributes =		USB_CONFIG_ATT_ONE,
-	.bMaxPower =		1,
+	.bMaxPower =		CONFIG_USB_GADGET_VBUS_DRAW / 2,
 };
 
 /* B.3.1  Standard AC Interface Descriptor */