usb: gadget: add support for multiple LUNs

Change-Id: Ia775a22c810960bbfd9184d8c77655b1e6b8a3d5
ruby: support multiple LUNs

Change-Id: I9ae93891f77f8469cfbb1c5ee876425992606c40
holiday: support multiple LUNs

Change-Id: I28e9572b0b2b9cb3a0de8934a0feb151f5f055be