dist/buildsystem_sanity_check: remove CPU_MODEL blacklists

Remove blacklisting the slwstk6000b and the cortexm.inc.mk as they must
be fixed.

dist/tools/buildsystem_sanity_check/check.sh

@@ -154,10 +154,6 @@ check_cpu_cpu_model_defined_in_makefile_features() {
     patterns+=(-e '^ *\(export\)\? *CPU_MODEL \??\?=')
     pathspec+=(':!boards/**/Makefile.features')
 
-    # Currently blacklist these non migrated file for CPU_MODEL
-    pathspec+=(':!boards/slwstk6000b/Makefile.include')
-    pathspec+=(':!makefiles/arch/cortexm.inc.mk')
-
     git -C "${RIOTBASE}" grep "${patterns[@]}" -- "${pathspec[@]}" \
             | error_with_message 'CPU and CPU_MODEL definition must be done by board/BOARD/Makefile.features or board/common/**/Makefile.features'
 }