kbuild: change filechk to surround the given command with { }

filechk_* rules often consist of multiple 'echo' lines. They must be
surrounded with { } or ( ) to work correctly. Otherwise, only the
string from the last 'echo' would be written into the target.

Let's take care of that in the 'filechk' in scripts/Kbuild.include
to clean up filechk_* rules.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/s390/tools/Makefile

@@ -25,7 +25,7 @@ define filechk_facility-defs.h
 endef
 
 define filechk_dis-defs.h
-	( $(obj)/gen_opcode_table < $(srctree)/arch/$(ARCH)/tools/opcodes.txt )
+	$(obj)/gen_opcode_table < $(srctree)/arch/$(ARCH)/tools/opcodes.txt
 endef
 
 $(kapi)/facility-defs.h: $(obj)/gen_facilities FORCE