devtool-source.bbclass: Do not create annotated tags if tag.gpgSign is set

devtool-source.bbclass: Do not create annotated tags if tag.gpgSign is set

If tag.gpgSign is configured in Git's configuration, then creating the
devtool-patched tag will fail (if Git's core.editor is not configured)
or it will hang (when trying to open the editor). This is beacause
tag.gpgSign causes git tag to create annotated tags. To avoid this,
specify --no-sign as argument to git tag.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>