linux511-rc-tkg: Enforce CFS CPU scheduler when using an alternative from .cfg.

We don't support alternative CPU schedulers on 5.11 just yet.

Fixes https://github.com/Frogging-Family/linux-tkg/issues/155

linux-tkg-config/prepare

@@ -206,6 +206,11 @@ _tkg_initscript() {
     echo "_custom_pkgbase=\"${_custom_pkgbase}\"" >> "${_path}"/cpuschedset
   fi
 
+  if [ "$_basever" = "511" ] && [ "$_cpusched" != "cfs" ]; then
+    warning "No support for alternative CPU schedulers on this kernel version. Defaulting to CFS."
+    echo "_cpusched=\"cfs\"" > "${_path}"/cpuschedset
+  fi
+
   case $_compileroptlevel in
 	"2")
 	_compileropt="-O3"