data-form: fix default type and text-multi detection
data-form: fix default type and text-multi detection

The type defaults to text-single regardless of the existance of a
<value> child.

Signed-off-by: Jonny Lamb <3d1fb3642aaab2ff70e3392a5ab916bf99eed6a3@collabora.co.uk>

noonien-d/wocky,freedesktop-unofficial-mirror/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky