loader: add loader_is_device_render_capable()

Add helper function to check if a device is render-capable.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24825>

src/loader/loader.h

@@ -50,6 +50,9 @@ int
 loader_open_render_node_platform_device(const char * const drivers[],
                                         unsigned int n_drivers);
 
+bool
+loader_is_device_render_capable(int fd);
+
 char *
 loader_get_render_node(dev_t device);