drm/i915: Remove unused debugfs/i915_emon_status

Before we start upon our great GT interrupt refactor, throw out the
cruft! In this case, it is an unloved debugfs showing the current ips
status, a fairly meaningless bunch of numbers that we are not checking.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190810090329.6966-1-chris@chris-wilson.co.uk