Create a macro to report the number of instances of the tuner driver
currently in use.  This will allow drivers to perform specific cleanups
before destroying the last instance of a tuner.
Signed-off-by: NMichael Krufky <mkrufky@linuxtv.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>