[PATCH v3][for 4.14] xhci: allow TRACE to work with EVENT ring dequeue

[David Laight]

From: Adam Wallis
> Sent: 25 September 2017 13:26
> inc_deq() currently bails earlier for EVENT rings than the common return
> point of the function, due to the fact that EVENT rings do not have
> link TRBs. The unfortunate side effect of this is that the very useful
> trace_xhci_inc_deq() function is not called/usable for EVENT ring
> debug.

Is it actually worth using different functions for the different
ring types?
>From what I remember there are conditionals in a lot of the functions
but they are fixed for most of the call sites.

	David