Add to readme instruction to create /dev/mei*

[jbagg]

Hi, it would be beneficial to know what kernel modules to load in order to use igsc.

[ausyskin]

Sorry, I do not want reproduce here whole driver stack that Intel Discrete Graphics requires. All major distros have it enabled, as I recall. It sounds that your disto lack, at least, INTEL_MEI_GSC config in it kernel.