platform/x86: thinkpad_acpi: Add 2nd Fan Support for Thinkpad P50

The Thinkpad P50 has 2 fans. Add the 2FAN quirk so the tpacpi driver
properly reports both fan speeds.
Because the P50 doesn't report the version of its EC controller,
we need to identify it by BIOS version (N1).

Signed-off-by: Alexander Kappner <agk@godking.net>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
[andy: renamed macro, massaged changelog]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>