drm/i915: drop intel_device_info_dump()

The debugfs, error state and regular dmesg logging dump needs seem to be
different. Remove the generic dump function only used for the welcome
message. This may be added back later when better abstractions are
identified, but at the moment this seems to be the simplest considering
the device info rework in progress. No longer rely on device info being
a substruct of dev_priv.

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/70ff0c7c0ec3ef8747af3c78e272b5a82be3d55b.1546267488.git.jani.nikula@intel.com