When `maxlen` is large (such as SIZE_MAX), the `end` pointer will overflow, causing strnlen() to incorrectly return 0. To not make the implementation over-complicated, fix the problem by using a counter. BUG=b:359951393 TEST=make unit-tests -j BRANCH=none Change-Id: Ic9d983b11391f5e05c2bceb262682aced5206f94 Signed-off-by: Yu-Ping Wu <yupingso@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/83914 Reviewed-by: Julius Werner <jwerner@chromium.org> Reviewed-by: Karthik Ramasubramanian <kramasub@google.com> Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>