lsm: clarify security_task_prctl() hook documentation

The task_prctl hook comment incorrectly described the hook as checking
whether a prctl operation is allowed. In reality, the hook exists for
LSMs to handle LSM-specific prctl operations.

Update the function description and kernel-doc comment to reflect the
actual behavior. The old wording appears to have been copied from other
permission-check hooks despite differing semantics.

Signed-off-by: Bill Roberts <bill.roberts@arm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
[PM: subj tweak, comment tweak -> "prctl to prctl()" ]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/security.c

@@ -3301,15 +3301,14 @@ int security_task_kill(struct task_struct *p, struct kernel_siginfo *info,
 }
 
 /**
- * security_task_prctl() - Check if a prctl op is allowed
+ * security_task_prctl() - Handle an LSM specific prctl() call
  * @option: operation
  * @arg2: argument
  * @arg3: argument
  * @arg4: argument
  * @arg5: argument
  *
- * Check permission before performing a process control operation on the
- * current process.
+ * Handle lsm specific prctl() operations.
  *
  * Return: Return -ENOSYS if no-one wanted to handle this op, any other value
  *         to cause prctl() to return immediately with that value.