kbuild: pkg: use -f $(srctree)/Makefile to recurse to top Makefile

'$(MAKE) KBUILD_SRC=' changes the working directory back and forth
between objtree and srctree.

It is better to recurse to the top-level Makefile directly.

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

scripts/package/buildtar

@@ -57,7 +57,7 @@ dirs=boot
 # Try to install modules
 #
 if grep -q '^CONFIG_MODULES=y' "${KCONFIG_CONFIG}"; then
-	make ARCH="${ARCH}" O="${objtree}" KBUILD_SRC= INSTALL_MOD_PATH="${tmpdir}" modules_install
+	make ARCH="${ARCH}" -f ${srctree}/Makefile INSTALL_MOD_PATH="${tmpdir}" modules_install
 	dirs="$dirs lib"
 fi