drm/i915: Add in-flight request details to intel_engine_dump()

In the intel_engine_cs dumper, we were showing the request details for
the request queue but not of those requests already passed to the hw
(just a summary of the seqno). If we show those details, we can then
eliminate the entirely redundant and forgotten debugfs/i915_gem_request

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171015204310.17045-1-chris@chris-wilson.co.uk


Reviewed-by: Jeff McGee <jeff.mcgee@intel.com>