PATCH v2 ASUS EC Sensors

[Eugene Shalygin]

This patchset replaces the HWMON asus_wmi_ec_sensors driver with
an implementation that does not use WMI but queries the embedded
controller directly.

That provides two enhancements: sensor reading became quicker (on some
systems or kernel configuration it took almost a full second to read
all the sensors, that transfers less than 15 bytes of data), the driver
became more fexible. The driver now relies on ACPI mutex to lock access
to the EC, in the same way as the WMI DSDT code does.

Changes in v2:
 - Replace sensor flags enum with bitset
 - Replace module init/probe functions with module_platform_driver_probe
   and ask the platform drivers framework to load the driver when ACPI
   EC is found (ACPI ID "PNP0C09").
 - Extend board data with BIOS version attribute for the mutex path to be
   BIOS version dependent.
 - Add module parameter to override the mutex path.