kbuild: use assignment instead of define ... endef for filechk_* rules

You do not have to use define ... endef for filechk_* rules.

For simple cases, the use of assignment looks cleaner, IMHO.

I updated the usage for scripts/Kbuild.include in case somebody
misunderstands the 'define ... endif' is the requirement.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index ec204fa..679e62e 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -201,9 +201,7 @@
 $(obj)/gconf.o: $(obj)/.gconf-cfg
 
 # check if necessary packages are available, and configure build flags
-define filechk_conf_cfg
-	$(CONFIG_SHELL) $<
-endef
+filechk_conf_cfg = $(CONFIG_SHELL) $<
 
 $(obj)/.%conf-cfg: $(src)/%conf-cfg.sh FORCE
 	$(call filechk,conf_cfg)