iw: small cleanup for the sizer code

We should use a signed variable if we subtract and potentially
end up with a negative value.

Additionally, we directly reference these variables so don't
need __attribute__((used)).

Change-Id: I78c2a5706dce9c90595284cf5e1d9d6f6fa1879e
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
1 file changed