Remove Warnings (ebpf)

[thiagoftsm]

Summary

This PR removes warnings when eBPF plugin is compiled.

Test Plan

1. Compile this Branch with the following CFLAGS and verify there is no warnings in plugin files:

CFLAGS="-O1 -ggdb -Wall -Wextra -fno-omit-frame-pointer -Wformat-signedness -fstack-protector-all -Wformat-truncation=2 -Wunused-result

Additional Information

For users: How does this change affect me?

[stelfrag]

One warning

ebpf_cachestat.c:717:72: warning: unused parameter ‘max_period’ [-Wunused-parameter]

[thiagoftsm]

One warning

Last commit address this, thank you!