drm/i915: Expose retry count to per gen reset logic

There is a possibility for per gen reset logic to
be more nasty if the softer approach on resetting does
not bear fruit.

Expose retry count to per gen reset logic if it
wants to take such tough measures.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180810140036.24240-1-mika.kuoppala@linux.intel.com