cifs-utils: add PACKAGECONFIG for cifsidmap

* cifs.idmap links with keyutils as log.do_package shows:
  DEBUG: cifs-utils: Dependency libkeyutils.so.1 requires package keyutils (used by files: /home2/mjansa/build/build-starfish-jethro/BUILD/work/h15-starfish-linux-gnueabi/cifs-utils/6.4-r0/packages-split/cifs-utils/usr/sbin/cifs.idmap)
* that causes following QA issue when keyutils are autodetected from
  sysroot:
  WARNING: QA Issue: cifs-utils rdepends on keyutils, but it isn't a build dependency? [build-deps]

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>