docs/platforms: Add S812L and S822L
docs/platforms: Add S812L and S822L

... because the model names are similar to the S8x2LC.

Signed-off-by: Jeremy Kerr <68a658b44bbaefab3ef5cd231967195fc0ff9d69@ozlabs.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

legoater/skiboot,legoater/skiboot,shenki/skiboot,stewart-ibm/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,open-power/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,stewart-ibm/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,stewart-ibm/skiboot