Revert "drm/i915: Don't use BAR mappings for ring buffers with LLC"

Revert "drm/i915: Don't use BAR mappings for ring buffers with LLC"

This reverts commit 4eb6789f9177a5fdb90e1b7cdd4b069d1fb9ce45 which is
commit 85636167e3206c3fbd52254fc432991cc4e90194 upstream.

It has been reported to cause problems on Alpine Linux and Manjaro Linux
5.15-based releases, so revert it for now until it can be sorted out.

Reported-by: "A.P. Jo." <apjo@tuta.io>
Link: https://lore.kernel.org/r/NQJqG8n--3-9@tuta.io
Link: https://gitlab.alpinelinux.org/alpine/aports/-/issues/14704
Reported-by: Philip Müller <philm@manjaro.org>
Link: https://lore.kernel.org/r/d955327b-cb1c-4646-76b9-b0499c0c64c6@manjaro.org
Link: https://gitlab.freedesktop.org/drm/intel/-/issues/8284
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v4.9+
Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>