With the FL2 slice files gone, update some of the hacking notes

Makefile

@@ -84,9 +84,7 @@ list_images:
 	$(info )
 	$(info $(basename $(wildcard *.d)))
 	$(info )
-	$(info The following make targets are available to produce FL2 files:)
-	$(info )
-	$(info $(foreach i,$(basename $(basename $(wildcard *.d))),$(basename $(wildcard $(i).*.FL2.slice))))
+	$(info Check the Descriptions.txt for the names of the known FL2 files)
 	$(info )
 	@true
 

docs/HACKING.txt

@@ -27,7 +27,10 @@ Makefile targets:
 If you expect to do development work, the following make targets are
 probably useful:
 
-    To list the available raw image files and FL2 files:
+    To list the available raw image files and FL2 files, check the
+    Descriptions.txt file for the list of known image names.  You
+    can also get a list of the "*.img.d" directories that contain
+    patches with this make command:
 
         make list_images
 
@@ -37,7 +40,7 @@ probably useful:
         make x230.G2HT35WW.img
 
     To just get the decrypted firmware file (with the same filename as
-    above), before any patches applied, the pseudo
+    above), before any patches applied:
 
         make x230.G2HT35WW.img.prepatch