fwi: adjust input size to meet timing constraints

The previous iniput size for both granularity and strong scaling tests
where too big to meet the timing constrains needed for garlic. This
patch sets a new, smaller, input size.

Also, a minor cleanup is applied to the rest of the fwi experiments
and figures.

garlic/apps/fwi/default.nix

@@ -34,6 +34,7 @@ stdenv.mkDerivation rec {
   # FIXME: Allow multiple MPI implementations
   postPatch = ''
     sed -i 's/= OPENMPI$/= INTEL/g' Makefile
+    sed -i 's/USE_O_DIRECT ?= NO/USE_O_DIRECT ?= YES/g' Makefile || true
   '';
 
   # FIXME: This is an ugly hack.