Support for Katana GF76-11UC, 17L2EMS1.108

[Waujito]

Support Katana GF76-11UC (#138)

List of changes:

• Support for reverse fan speed.
  On tihs platform fan speed is reversed (more value in ec -> less fan speed). This PR adds a workaround for this problem without break of existing APIs.
  A one problem keeps: In fact fan speed takes 2 bytes (for me, 0xc8 and 0xc9) but the module supports only one byte (0xc9). On my laptop CPU fan speed is inversed so when fan gets slow it turns out to be (0x00 0xfa -> 0x00 0xff -> 0x01 0x08) Which may lead to EINVAL (when it reads 0x08 and compares it with maximum speed). But this is not critical because such a big value is reported for about 1 second and only when fan is about to stop and become 0x00 0x00.
• Fix keyboard brightness reset on module exit. By default kernel triggers the setter on led_classdev_unregister which leads to keyboard brightness reset (the keyboard backlight turns off). This behavior may cause resets every system reboot. Also it's quite annoying in development.

[glpnk]

You shouldn't use RPM values, this thing is broken by design.

Technically, you can add RPM values and read them separately. This also will require separating %RPM and RPM addresses, which was broken when EC map was badly researched

[Waujito]

As the driver with support for fan speed in sensors is out, I think this PR is obsolete. The only thing I want to keep is Fix keyboard brightness reset on module exit. commit because it is annoying to see light swithces for keyboard backlight when the driver exists.