platform/x86: toshiba_acpi: Convert ACPI driver to a platform one

platform/x86: toshiba_acpi: Convert ACPI driver to a platform one

In all cases in which a struct acpi_driver is used for binding a driver
to an ACPI device object, a corresponding platform device is created by
the ACPI core and that device is regarded as a proper representation of
underlying hardware.  Accordingly, a struct platform_driver should be
used by driver code to bind to that device.  There are multiple reasons
why drivers should not bind directly to ACPI device objects [1].

Overall, it is better to bind drivers to platform devices than to their
ACPI companions, so convert the Toshiba Laptop ACPI Extras driver from
an ACPI driver to a platform one.

After this change, all of the subordinate hwmon, IIO, and LED class
devices will be registered under the platform device used for driver
binding instead of its ACPI companion.

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

However, the sysfs attributes in toshiba_attr_group will still be there
in the sysfs directory of the ACPI companion of the platform device used
for driver binding to maintain backwards compatibility with possibly
existing user space utilities depending on the presence of those
attributes.

Link: https://lore.kernel.org/all/2396510.ElGaqSPkdT@rafael.j.wysocki/
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/2269772.irdbgypaU6@rafael.j.wysocki
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>