Send also a packet containing an ABORT chunk in response to an OOTB packet
containing a COOKIE-ECHO chunk.

MFC after: 3 days
Remove uncessary cache and TLB maintenance ops.

 - These were needed on armv4/5 (VIVT cache), not needed on armv6.
 - The wbinv_all call can't be used on SMP systems; cache operations by
   set/way are not broadcast to other cores.
 - The TLB maintenance operations needed for pmap_growkernel() happen in
   pmap_grow_l2_bucket(), so there's no need to flush all TLB entries at
   the end.
 - There may not be any need for the TLB flush at the beginning of
   pmap_release(), but it's left in for now pending more investigation.

Pointed out by:	   Svatopluk Kraus <onwahe@gmail.com>
Discussed with:	   cognet@