Draft: [arm64,ppc64*] Disable broken graphics drivers when using non-4 kiB pages
nouveau is long known to only work with 4 kiB pages (bug #790690), but lacks a Kconfig dependency to enforce this.
xe is also known to only work with 4 kiB pages (bug #1109776) and again lacks a Kconfig dependency. There are patches that may fix this soon, but they have not yet landed.
Explicitly disable both of these in the config fragments that set different page sizes.
Edited by Ben Hutchings