First pile for 4.14:

- cnl fixes (Rodrigo, Manasi)
- per-engine reset support aka TDR (Michel Thierry)
- dynamic DPCD backlight support (Puthikorn Voravootivat)
- prep for huge gpu pages (Matthew Auld)
- make contexts less BKL dependent (Chris)
- bunch of execlist/gem corner-cases fixes and locking down
  self-checks (Chris)
- fix waitboost accounting when using fence waits (Chris)
- clean up PCH detection/handling (Ville)
- usual pile of small fixes and cleanups