Add support for Asus G75VX and Geforce GTX 670MX

I used the commands you described in the comments above nvidiabl-gpu.h and nvidiabl-laptops.h to implement support for the Geforce GTX 670MX and the Asus G75VX.

The backlight is now working for me, but the automatic min/max detection is faulty. I had to manually specify a maximum of 0x20000 (the autodetection chose 0x606).