USB: gadget: gadget_is_{dualspeed,otg} predicates and cleanup

This adds two small inlines to the gadget stack, which will
often evaluate to compile-time constants.  That can help
shrink object code and remove #ifdeffery.

 - gadget_is_dualspeed(), currently always a compile-time
   constant (depending on which controller is selected).

 - gadget_is_otg(), usually a compile time "false", but this
   is a runtime test if the platform enables OTG (since it's
   reasonable to populate boards with different USB sockets).

It also updates two peripheral controller drivers to use these:

 - fsl_usb2_udc, mostly OTG-related bugfixes:  non-OTG devices
   must follow the rules about drawing VBUS power, and OTG ones
   need to reject invalid SET_FEATURE requests.

 - omap_udc, just scrubbing a bit of #ifdeffery.

And also gadgetfs, which lost some #ifdefs and moved to a more
standard handling of DEBUG and VERBOSE_DEBUG.

The main benefits come from patches which will follow.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>