ACPI: NFIT: Remove unnecessary .remove callback

The ACPI NFIT driver provides an empty function as it's .remove() callback
which is not necessary, so drop the empty acpi_nfit_remove() and the
.remove() callback initialization from it.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>