modetest: add support for DRM_FORMAT_NV{24,42}
Add support for semi-planar YUV formats with non-subsampled chroma planes.
This has been tested with the shmob_drm driver on the R-Mobile A1-based Atmark Techno Armadillo-800-EVA development board.
https://lore.kernel.org/r/cover.1688570702.git.geert+renesas@glider.be/