usb: kconfig: create a menu for usb

With recent additions to USB Kconfig the number of USB options had grown
large enough to warrant a separate menu for USB.

Add a Kconfig menu for USB.

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: NNikita Kiryanov <nikita@compulab.co.il>

drivers/usb/Kconfig

+menu USB
 config USB_ARCH_HAS_HCD
 	def_bool y
 
@@ -87,3 +88,4 @@ endchoice
 endif
 
 endif
+endmenu