fetch2: wget latest_versionstring improvments in get version by dir

fetch2: wget latest_versionstring improvments in get version by dir

Add support for scan every version directory using _check_latest_version
makes code more robust because sometimes upstream projects publish
new directories without files, causing don't find version.

To support this new behaviour remove _check_latest_dir and replace for
_check_latest_version_by_dir,

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>