devtool: update-recipe: find and use existing files directories

devtool: update-recipe: find and use existing files directories

devtool update-recipe was defaulting to the ${BPN} named directory when
adding patches next to a recipe, but that meant if you already had files
in a ${BP} named directory (i.e. name and version) or "files" then you'd
end up with two directories next to the recipe, which is usually not
what you want. To avoid this, look through FILESPATH and take the first
one that's the same level or one level down from the recipe and already
exists, if any.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>