ACPI: fan: Optimize struct acpi_fan_fif

We don't need u64 to store the information about _FIF. There are two
booleans (fine_grain_ctrl and low_speed_notification) and one field
step_size which can take value from 1-9. There are no internal users
of revision field. So convert all fields to u8, by not directly
extracting the _FIF info the struct. Use an intermediate buffer to
extract and assign.

This will help to do u32 math using these fields. No functional
changes are expected.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>