[PATCH] drm/panel: make drm_panel.h self-contained

[Sam Ravnborg]

Hi Jani.

On Thu, Jun 27, 2019 at 02:01:03PM +0300, Jani Nikula wrote:
> Fix build warning if drm_panel.h is built with CONFIG_OF=n or
> CONFIG_DRM_PANEL=n and included without the prerequisite err.h:
> 
> ./include/drm/drm_panel.h: In function ‘of_drm_find_panel’:
> ./include/drm/drm_panel.h:203:9: error: implicit declaration of function ‘ERR_PTR’ [-Werror=implicit-function-declaration]
>   return ERR_PTR(-ENODEV);
>          ^~~~~~~
> ./include/drm/drm_panel.h:203:9: error: returning ‘int’ from a function with return type ‘struct drm_panel *’ makes pointer from integer without a cast [-Werror=int-conversion]
>   return ERR_PTR(-ENODEV);
>          ^~~~~~~~~~~~~~~~
> 
> Fixes: 5fa8e4a22182 ("drm/panel: Make of_drm_find_panel() return an ERR_PTR() instead of NULL")
> Cc: Boris Brezillon <boris.brezillon at bootlin.com>
> Cc: Thierry Reding <treding at nvidia.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Reviewed-by: Sam Ravnborg <sam at ravnborg.org>

When we start to deploy headers-test I expect us to find many more of
this class of issues.
But lets get them fixed so we do not see sporadic build errors due
to missing dependencies in the header files.

I assume you will commit the fix.

	Sam