package/perftest: fix unmet direct dependencies

Since it was iontroduced in commit d4ecefa3 (package/perftest: new
package), perftest was missing the reverse dependency on the kernel
headers version inherited from rdma-core.

In commit 3279d8b9 (package/rdma-core: needs NPTL), the dependency
of rdma-core on NTPL was not propagated to its reverse dependencies,
notably perftests.

Fixes:
  - http://autobuild.buildroot.net/results/00c/00ce19a1589c6028ee77c333ed9107e2c8c8d6de


  - d4ecefa3
  - 3279d8b9

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
[yann.morin.1998@free.fr:
  - also add misisng headers dependency
  - expand commit log
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>