Mention Red Hat kernel headers package name
Move private definitions to mimicking headers

Move definitions from private headers from hid-huion.c to header files
with pathnames matching those used by the hid sub-tree in the kernel.

This removes unnecessary differences to the mainline version of
hid-huion.c.
Update hid-huion.c copyright year
Protect against division by zero resolution
Don't use zeroing alloc unnecessarily
Don't zero drvdata after a zeroing alloc
Move parameter extraction comments closer to the code
Don't filter by PID needlessly in huion_raw_event
Use buf type appropriate for LE data
Link to the superseeded huion-driver