mkdisk.sh: 24M is an acceptable minimum

util/mkdisk.sh

@@ -12,8 +12,8 @@ SPACE_REQ=$(du -sb "$DIR/../fatbase" | cut -f 1)
 let "SIZE = ($SPACE_REQ / 1040000)"
 
 # Minimum size
-if [ $SIZE -lt 32 ]; then
-    SIZE=32
+if [ $SIZE -lt 24 ]; then
+    SIZE=24
 fi
 
 # Use more sectors-per-cluster for larger disk sizes