drm/i915: debugfs spring cleaning

Just like with sysfs, we do some major overhaul.

Pass dev_priv instead of dev to all feature macros (IS_, HAS_,
INTEL_, etc.). This has the side effect that a bunch of functions
now get dev_priv passed instead of dev.

All calls to INTEL_INFO()->gen have been replaced with
INTEL_GEN().

We want access to to_i915(node->minor->dev) in a lot of places,
so add the node_to_i915() helper to accommodate for this.

Finally, we have quite a few cases where we get a void * pointer,
and need to cast it to drm_device *, only to run to_i915() on it.
Add cast_to_i915() to do this.

v2: Don't introduce extra dev (Chris)

v3: Make pipe_crc_info have a pointer to drm_i915_private instead of
    drm_device. This saves a bit of space, since we never use
    drm_device anywhere in these functions.

    Also some minor fixup that I missed in the previous version.

v4: Changed the code a bit so that dev_priv is passed directly
    to various functions, thus removing the need for the
    cast_to_i915() helper. Also did some additional cleanup.

v5: Additional cleanup of newly introduced changes.

v6: Rebase again because of conflict.

Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160822105931.pcbe2lpsgzckzboa@boom


Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>