cpu_map: Suggest better command for updating test data files

cpu-cpuid.py was merged into cpu-gather.py and the script can handle
multiple files so there's no need for a loop around it.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

src/cpu_map/x86_features.xml

@@ -1,9 +1,8 @@
 <!--
   After adding new features, update existing test files with
 
-    for json in tests/cputestdata/x86_64-cpuid-*.json; do
-      tests/cputestdata/cpu-cpuid.py diff $json
-    done
+    tests/cputestdata/cpu-gather.py diff tests/cputestdata/x86_64-cpuid-*.json
+
 -->
 <cpus>
   <!-- standard features, EDX -->