drm/i915: Move i915_check_and_clear_faults to intel_reset.c

The code is logically about reset so it makes sense.

It also enables making i915_clear_error_registers static.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607115932.20271-1-tvrtko.ursulin@linux.intel.com