kbuild: fix "tools-all" target

The top Makefile must export HOST_TOOLS_ALL to use it
in tools/Makefile.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Tested-by: Heiko Schocher <hs@denx.de>
Acked-by: Heiko Schocher <hs@denx.de>
1 file changed