tools/testing/nvdimm: add watermarks for dax_pmem* modules

Add nfit_test 'watermarks' for the dax_pmem, dax_pmem_core, and
dax_pmem_compat modules. This causes the nfit_test module to fail
loading in case any of these modules are also not overridden with the
ldconfig wrapped modules. Without this, nfit_test would sometimes fail
creation of device-dax namespaces on the nfit_test_bus with an unhelpful
error log such as:

    dax_pmem dax5.0: could not reserve metadata
    dax_pmem: probe of dax5.0 failed with error -16

Which was caused due to the unwrapped version of
devm_request_mem_region() being called.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>