prevents the unfortunate situation whereby one might kldload a firmware
module by hand and later kldunload it while a driver still has an open
reference to it.
MFC after: 1 week
Glanced at by: iedowse
specially crafted module. There are several handrolled sollutions to this
problem in the tree already which will be replaced with this. They include
iwi(4), ipw(4), ispfw(4) and digi(4).
No objection from: arch
MFC after: 2 weeks
X-MFC after: some drivers have been converted