drm/i915: Move OA files to separate folder

OA files look to be auto-generated so we can keep them all in
dedicated subdirectory.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190626123826.39760-1-michal.wajdeczko@intel.com