drm/xe: Allow error injection for xe_pxp_exec_queue_add

This will allow us to simulate this function returning an error like
we do for other functions called in the exec_queue_create path.

Signed-off-by: Daniele Ceraolo Spurio <[e-mail]>
Cc: John Harrison <[e-mail]>
Reviewed-by: John Harrison <[e-mail]>
Signed-off-by: John Harrison <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/xe/xe_pxp.c

···
 
 	return ret;
 }
+ALLOW_ERROR_INJECTION(xe_pxp_exec_queue_add, ERRNO);
 
 static void __pxp_exec_queue_remove(struct xe_pxp *pxp, struct xe_exec_queue *q, bool lock)
 {