acpi/nfit: Update NFIT flags error message

ACPI NFIT flags field reports major errors on NVDIMM, which need
user's attention.

Update the current log to a proper error message with dev_err().
The current message string is kept for grep-compatibility.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>