[PATCH RESEND] usb: mtu3: don't run gadget completion callbacks with interrupts disabled

[Ryan Brue]

Hi Greg,

Gentle ping on this one too. Similarly has had no comments since the 
resend on the 29th of September.

It fixes the softirq WARN in the commit message, which any gadget 
function that reaches netif_rx() (u_ether in this case) hits on mtu3.

Thanks,
Ryan Brue