drm/i915/pxp: Implement PXP irq handler

The HW will generate a teardown interrupt when session termination is
required, which requires i915 to submit a terminating batch. Once the HW
is done with the termination it will generate another interrupt, at
which point it is safe to re-create the session.

Since the termination and re-creation flow is something we want to
trigger from the driver as well, use a common work function that can be
called both from the irq handler and from the driver set-up flows, which
has the addded benefit of allowing us to skip any extra locks because
the work itself serializes the operations.

v2: use struct completion instead of bool (Chris)
v3: drop locks, clean up functions and improve comments (Chris),
    move to common work function.
v4: improve comments, simplify wait logic (Rodrigo)
v5: unconditionally set interrupts, rename state_attacked var (Rodrigo)
v10: remove inclusion of intel_gt_types.h from intel_pxp.h (Jani)

Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
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>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924191452.1539378-10-alan.previn.teres.alexis@intel.com