tools: rename to 'utils'
After some discussion, we found out that "tools" has the four first letters identical to the "toolchain" subfolder, which makes it a bit unpractical with tab-completion. So, this commit renames "tools" to "utils", which is more tab-completion-friendly. This has been discussed with Arnout and Yann. Signed-off-by: Thomas Petazzoni <firstname.lastname@example.org>