readline: remove redundant BR2_PACKAGE_READLINE_HEADERS configuration

Header files on target is globally controlled by BR2_HAVE_DEVFILES.

package/readline/Config.in

@@ -9,10 +9,3 @@ config BR2_PACKAGE_READLINE_TARGET
 	depends on BR2_READLINE
 	help
 	  Say yes here to install the readline libraries on the target.
-
-config BR2_PACKAGE_READLINE_HEADERS
-	bool "readline headers for the target"
-	depends on BR2_PACKAGE_READLINE_TARGET
-	help
-	  Say yes here to install the readline headers and documentation
-	  on the target.

package/readline/readline.mk

@@ -75,9 +75,6 @@ $(TARGET_DIR)/$(READLINE_TARGET_SHARED_BINARY): $(READLINE_DIR)/$(READLINE_BINAR
 		-C $(READLINE_DIR) install-shared uninstall-doc
 	chmod 775 $(TARGET_DIR)/usr/lib/libreadline.so.$(READLINE_VERSION) $(TARGET_DIR)/usr/lib/libhistory.so.$(READLINE_VERSION)
 	$(STRIPCMD) $(TARGET_DIR)/usr/lib/libreadline.so.$(READLINE_VERSION) $(TARGET_DIR)/usr/lib/libhistory.so.$(READLINE_VERSION)
-ifneq ($(BR2_PACKAGE_READLINE_HEADERS),y)
-	rm -rf $(TARGET_DIR)/usr/include/readline
-endif
 
 readline: ncurses $(STAGING_DIR)/usr/include/readline/readline.h