drm/xe/hwmon: expose fan speed

Add hwmon support for fan1_input, fan2_input and fan3_input attributes,
which will expose fan speed of respective channels in RPM when supported
by hardware. With this in place we can monitor fan speed using lm-sensors
tool.

v2: Rely on platform checks instead of mailbox error (Aravind, Rodrigo)
v3: Introduce has_fan_control flag (Rodrigo)

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250312085909.755073-1-raag.jadav@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>