drm/xe/pxp: do not queue unneeded terminations from debugfs

The PXP terminate debugfs currently unconditionally simulates a
termination, no matter what the HW status is. This is unneeded if PXP is
not in use and can cause errors if the HW init hasn't completed yet.
To solve these issues, we can simply limit the terminations to the cases
where PXP is fully initialized and in use.

v2: s/pxp_status/ready/ to avoid confusion with pxp->status (John)

Fixes: 385a8015 ("drm/xe/pxp: Add PXP debugfs support")
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4749


Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://lore.kernel.org/r/20250416201622.1295369-1-daniele.ceraolospurio@intel.com