binder: cleanup unsafe in unsafe fns warning (E0133)

[ojeda]

We enabled the warnings in #339 and we would like to move it to hard error, so we need to clean them up.

warning: call to unsafe function is unsafe and requires unsafe block (error E0133)
  --> drivers/android/node.rs:86:20
   |
86 |               inner: SpinLock::new(NodeDeathInner {
   |  ____________________^
87 | |                 dead: false,
88 | |                 cleared: false,
89 | |                 notification_done: false,
90 | |                 aborted: false,
91 | |             }),
   | |______________^ call to unsafe function