dt-bindings: panel: rocktech,jh057n00900: Modernize

- Use common properties from panel-common.yaml
- Indent comment like content
- Don't preserve newlines in description
- Indent example by four spaces

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/60639e670028af7e8ab31379256ba331a1bdf6cc.1597561897.git.agx@sigxcpu.org