rust: task: use safe current! macro

Refactor the `Task::pid_in_current_ns()` to use the safe abstraction
`current!()` instead of the unsafe `bindings::get_current()` binding.

Signed-off-by: Antonio Hickey <[email protected]>

rust/kernel/task.rs

@@ -164,7 +164,7 @@ impl Task {
     /// Returns the given task's pid in the current pid namespace.
     pub fn pid_in_current_ns(&self) -> Pid {
         // SAFETY: Calling `task_active_pid_ns` with the current task is always safe.
-        let namespace = unsafe { bindings::task_active_pid_ns(bindings::get_current()) };
+        let namespace = unsafe { bindings::task_active_pid_ns(current!()) };
         // SAFETY: We know that `self.0.get()` is valid by the type invariant.
         unsafe { bindings::task_tgid_nr_ns(self.0.get(), namespace) }
     }