Split the kmod-video-dma into kmod-video-dma-sg and
kmod-video-dma-contig. The old one contained two kmods, but sometimes
only one of them is build which caused problems. The configuration
options are not manually selectable in the kernel and hidden in OpenWrt.
Currently this causes build failures on some targets.
Fixes: 4d7cbe0a55 ("kernel: video-dma: explicitly state packaged modules")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>