Input: initialize device counter variables with -1

Let's initialize atomic_t variables keeping track of number of various
devices created so far with -1 in order to avoid extra subtraction
operation.

Change-Id: I58bfb094ec24e4b4cab48b3318852a27a227dc9a
Signed-off-by: Aniroop Mathur <aniroop.mathur@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Tim Clark <tim.clark.82@gmail.com>