USB: Move usb/mon/ up to misc options in Kconfig

This makes "USB Monitor" appear under "Miscellaneous USB options"
section instead of in the middle of device specific drivers in the
"USB Imaging devices" section.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>