drm/i915/pxp: Implement arb session teardown

Teardown is triggered when the display topology changes and no
long meets the secure playback requirement, and hardware trashes
all the encryption keys for display. Additionally, we want to emit a
teardown operation to make sure we're clean on boot and resume

v2: emit in the ring, use high prio request (Chris)
v3: better defines, stalling flush, cleaned up and renamed submission
    funcs (Chris)
v12: fix uninitialized variable bug

Signed-off-by: Huang, Sean Z <sean.z.huang@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924191452.1539378-9-alan.previn.teres.alexis@intel.com