configure, meson: move CONFIG_HOST_DSOSUF to Meson

This is just a constant string, there is no need to pass it in config-host.mak.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211007130829.632254-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>