platform/x86: toshiba_acpi: Add fan RPM reading (hwmon interface)

This expands on the previous commit, exporting the fan RPM via hwmon.

This will look something like the following when using the "sensors"
command from lm_sensors:

toshiba_acpi_sensors-acpi-0
Adapter: ACPI interface
fan1:           0 RPM

Signed-off-by: Arvid Norlander <lkml@vorpal.se>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220902174018.1720029-3-lkml@vorpal.se


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>