ACPI: NFIT: core: Convert the driver to a platform one

ACPI: NFIT: core: Convert the driver to a platform one

While binding drivers directly to struct acpi_device objects allows
basic functionality to be provided, at least in the majority of cases,
there are some problems with it, related to general consistency, sysfs
layout, power management operation ordering, and code cleanliness.

Overall, it is better to bind drivers to platform devices than to their
ACPI companions, so convert the ACPI NFIT core driver to a platform one.

While this is not expected to alter functionality, it changes sysfs
layout and so it will be visible to user space.

This change was mostly developed by Michal Wilczynski [1].

Linu: https://lore.kernel.org/linux-acpi/20231011083334.3987477-6-michal.wilczynski@intel.com/ [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/6221453.lOV4Wx5bFT@rafael.j.wysocki
Acked-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Ira Weiny <ira.weiny@intel.com>