Add support for Exar XR17V358 8-port serial device to puc(4)

Reviewed by:	marius
Sponsored by:	Sandvine Inc.
MFC after:	1 week
Fix two bugs:

* when pulling frames off of the TID queue, the ATH_TID_REMOVE()
  macro decrements the axq_depth field.  So don't do it twice.

* in ath_tx_comp_cleanup_aggr(), bf wasn't being reset to bf_first
  before walking the buffer list to complete buffers; so those buffers
  will leak.
Add a few examples.

Obtained from:	OpenBSD
Why'd I keep this here? remove it entirely now.