Makefile: revert "Makefile: Document ability to make file.lst and file.S" partially

Commit 6271897978 ("Makefile: Document ability to make file.lst
and file.S") document ability to make file.S, but there isn't such
ability in kbuild, so revert it.

Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>

Makefile

@@ -1265,7 +1265,7 @@ help:
 	@echo  '  firmware_install- Install all firmware to INSTALL_FW_PATH'
 	@echo  '                    (default: $$(INSTALL_MOD_PATH)/lib/firmware)'
 	@echo  '  dir/            - Build all files in dir and below'
-	@echo  '  dir/file.[oisS] - Build specified target only'
+	@echo  '  dir/file.[ois]  - Build specified target only'
 	@echo  '  dir/file.lst    - Build specified mixed source/assembly target only'
 	@echo  '                    (requires a recent binutils and recent build (System.map))'
 	@echo  '  dir/file.ko     - Build module including final link'