[PATCH] drm: check drm_format_info hsub and vsub to avoid divide by zero

[Brian Starkey]

Hi,

On Fri, Oct 29, 2021 at 09:15:28AM -0400, George Kennedy wrote:
> 
> Asking if you have any input on how to deal with hsub and vsub = zero?

That's just a straight mistake on those formats - they should
be 1. My bad for not spotting it in review.

On the one hand, having formats in this table is a nice
machine-readable way to describe them. On the other, as drm_fourcc is
being used as the canonical repository for formats, including ones
not used in DRM, we can end up with situations like this.
(R10/R12 being another example of formats not used in DRM:
20211027233140.12268-1-laurent.pinchart at ideasonboard.com)

Thanks,
-Brian