testing/nvdimm: Add test module for non-nfit platforms

testing/nvdimm: Add test module for non-nfit platforms

The current test module cannot be used for testing platforms (make check)
that do not have support for NFIT. In order to get the ndctl tests working,
we need a module which can emulate NVDIMM devices without relying on
ACPI/NFIT.

The aim of this proposed module is to implement a similar functionality to
the existing module but without the ACPI dependencies.

This RFC series is split into reviewable and compilable chunks.

This patch adds a new driver and registers two nvdimm bus needed for ndctl
make check.

Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Link: https://lore.kernel.org/r/20201222042240.2983755-2-santosh@fossix.org
Signed-off-by: Dan Williams <dan.j.williams@intel.com>