drm/i915: Stop getting the fault address from RING_FAULT_REG

drm/i915: Stop getting the fault address from RING_FAULT_REG

This register does not contain it. Instead, we have to look into FAULT_TLB_DATA0 & 1
(where, by the way, we can also get the address space).

v2: Right formatting
v3:
  - Use 12 (as per the register format) instead of PAGE_SIZE (Chris)
  - s/BITS_44_TO_47/HIGHBITS (Chris)
  - Right formatting, this time for real

Fixes: b03ec3d67ab8 ("drm/i915: There is only one fault register from GEN8 onwards")
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1513982329-32191-1-git-send-email-oscar.mateo@intel.com
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>