drm/i915: Shortcut readiness to reset check

If the engine says it is ready for reset, it is ready
so avoid further dancing and proceed.

v2: reg (Chris)
v3: request, ack, mask from following patch (Chris)

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>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190412165335.16347-1-mika.kuoppala@linux.intel.com