[PATCH] doc: fix Sphinx build without RTD theme

[Thomas Monjalon]

17/10/2024 19:14, Thomas Monjalon:
> DTS is using a specific configuration of Sphinx
> which is supported only with the theme Read The Docs.
> If not available, this error may be seen:
> 	unsupported theme option 'collapse_navigation' given
> 
> In order to allow doc generation without this theme,
> a check is added to make the specific configuration optional.
> 
> Fixes: 7f9326423a04 ("dts: add API doc generation")
> 
> Signed-off-by: Thomas Monjalon <thomas at monjalon.net>
> Signed-off-by: Robin Jarry <rjarry at redhat.com>

Was applied quickly to fix the build.