module-init-tools: check correct symbol for cross-depmod

Reported by Markus Heidelberg

package/module-init-tools/module-init-tools.mk

@@ -109,7 +109,7 @@ cross-depmod26-clean:
 cross-depmod26-dirclean:
 	rm -rf $(MODULE_INIT_TOOLS_DIR2)
 
-ifeq ($(strip $(CONFIG_BR2_PACKAGE_LINUX)),y)
+ifeq ($(strip $(BR2_PACKAGE_LINUX)),y)
 HOST_SOURCE+=module-init-tools-source
 endif