USB: goku_udc trivial cleanups

Minor fixes to goku_udc ... whitespace, let -DDEBUG do its thing,
check the return value of device_register(), sparse tweaks.

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