target_files: copy to PRODUCT-SERVICES instead

The add_img_to_target_files.py script uses upper() to determine
the name of sub-directory under target_files_intermediates. The
name of the image is product-services.img but the sub-directory
name was PRODUCT_SERVICES. Change it to PRODUCT-SERVICES so that
'm dist' works.

Test: m dist
Change-Id: I8cad841c674b5d62c1d803d0383fc3aee14f272a
diff --git a/core/Makefile b/core/Makefile
index ae8a30a..78759ae 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2999,7 +2999,7 @@
 ifdef BOARD_PRODUCT_SERVICESIMAGE_FILE_SYSTEM_TYPE
 	@# Contents of the product-services image
 	$(hide) $(call package_files-copy-root, \
-		$(TARGET_OUT_PRODUCT_SERVICES),$(zip_root)/PRODUCT_SERVICES)
+		$(TARGET_OUT_PRODUCT_SERVICES),$(zip_root)/PRODUCT-SERVICES)
 endif
 ifdef INSTALLED_SYSTEMOTHERIMAGE_TARGET
 	@# Contents of the system_other image