test/hash: add missing file in meson build

The test_hash_readwrite.c was not in the meson.build file. This
commit adds the missing test into the file.

Fixes: 0eb3726ebcf1 ("test/hash: add test for read/write concurrency")
Cc: stable@dpdk.org
Signed-off-by: Yipeng Wang <yipeng1.wang@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>