libnvdimm: Introduce CONFIG_NVDIMM_SECURITY_TEST flag

nfit_test overrode the security_show() sysfs attribute function in nvdimm
dimm_devs in order to allow testing of security unlock. With the
introduction of CXL security commands, the trick to override
security_show() becomes significantly more complicated. By introdcing a
security flag CONFIG_NVDIMM_SECURITY_TEST, libnvdimm can just toggle the
check via a compile option. In addition the original override can can be
removed from tools/testing/nvdimm/.

The flag will also be used to bypass cpu_cache_invalidate_memregion() when
set in a different commit. This allows testing on QEMU with nfit_test or
cxl_test since cpu_cache_has_invalidate_memregion() checks whether
X86_FEATURE_HYPERVISOR cpu feature flag is set on x86.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166983618758.2734609.18031639517065867138.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>