s390: drop redundant directory creation from tools Makefile

As you can see in scripts/Kbuild.include, the filechk creates the
parent directory of the target as needed.

This Makefile does not need to explicitly create the directory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>