Use constant for cookie instead of value.

Usually '0' cookie is used for 'I dont care' but this cookie
is used and intended to coincide the value of a constexpr
elsewhere in the code. Noticed while working on b/67479818.

Test: hidl's run_all_device_tests.sh
Change-Id: Ib591b5bc9d221ae03ab7b33e8d831ad72134f087
1 file changed