ACPI: fan: Add fan speed reporting for fans with only _FST

ACPI: fan: Add fan speed reporting for fans with only _FST

Add support for ACPI fans with _FST to report their speed even if they do
not support fan control.

As suggested by Armin Wolf [1] and per the Windows Thermal Management
Design Guide [2], Samsung Galaxy Book series devices (and possibly many
more devices where the Windows guide was strictly followed) only implement
the _FST method and do not support ACPI-based fan control.

Currently, these fans are not supported by the kernel driver but this patch
will make some very small adjustments to allow them to be supported.

This patch is tested and working for me on a Samsung Galaxy Book2 Pro whose
DSDT (and several other Samsung Galaxy Book series notebooks which
currently have the same issue) can be found at [3].

Link: https://lore.kernel.org/platform-driver-x86/53c5075b-1967-45d0-937f-463912dd966d@gmx.de
Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/design-guide
Link: https://github.com/joshuagrisham/samsung-galaxybook-extras/tree/8e3087a06b8bdcdfdd081367af4b744a56cc4ee9/dsdt
Signed-off-by: Joshua Grisham <josh@joshuagrisham.com>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Link: https://patch.msgid.link/20250222094407.9753-1-josh@joshuagrisham.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>