Not sure if our compiler supports a __counted_by__ attribute andAdd checks for __counted_by(_x) and __nonstring as and depending
how to check for it, so define __counted_by() to nothing for now
on compiler support enable the attribute/feature.
This is needed to make mt76k76 and ath1xk drivers to compile.
Sposnored by: The FreeBSD Foundation
MFC after: 3 days