i8k: Add support for fan labels

This patch adds labels support for fans if SMM function with EAX register
0x03a3 reports it. This information was taken from DOS binary NBSVC.MDM.

Additionally this patch change detection of fan presece. Instead reading fan
status now detection is based on new label SMM function. Dell DOS binary
NBSVC.MDM is doing similar checks, so we should do that too.

This patch also remove I8K_FAN_LEFT and I8K_FAN_RIGHT usage from hwmon driver
part because that names does not make sense anymore. So numeric constants are
used instead. Original /proc/i8k ioctl part was not changed for compatibility
reasons.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>