kbuild: move coccicheck help from scripts/Makefile.help to top Makefile

In my view, it is not helpful to have a separate file just for
the coccicheck help message.  Merge scripts/Makefile.help into
the top-level Makefile.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>

Makefile

@@ -1384,7 +1384,7 @@ help:
 	@echo  '  export_report   - List the usages of all exported symbols'
 	@echo  '  headers_check   - Sanity check on exported headers'
 	@echo  '  headerdep       - Detect inclusion cycles in headers'
-	@$(MAKE) -f $(srctree)/scripts/Makefile.help checker-help
+	@echo  '  coccicheck      - Check with Coccinelle'
 	@echo  ''
 	@echo  'Kernel selftest:'
 	@echo  '  kselftest       - Build and run kernel selftest (run as root)'