Make arm spline definition a ton easier

Remove all the redundant intermediate variables.

Change-Id: I1e1d93b8a4363f3498775a0eead3d14ae190e77a
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2023/control_loops/superstructure/arm/arm.cc b/y2023/control_loops/superstructure/arm/arm.cc
index fd265c4..03a1b21 100644
--- a/y2023/control_loops/superstructure/arm/arm.cc
+++ b/y2023/control_loops/superstructure/arm/arm.cc
@@ -38,7 +38,7 @@
       search_graph_(MakeSearchGraph(&dynamics_, &trajectories_, alpha_unitizer_,
                                     kVMax(), &hybrid_roll_joint_loop_)),
       // Go to the start of the first trajectory.
-      follower_(&dynamics_, &hybrid_roll_joint_loop_, NeutralPosPoint()),
+      follower_(&dynamics_, &hybrid_roll_joint_loop_, NeutralPoint()),
       points_(PointList()),
       current_node_(0) {
   int i = 0;
@@ -92,7 +92,7 @@
   }
 
   // TODO(milind): should we default to the closest position?
-  uint32_t filtered_goal = arm::NeutralPosIndex();
+  uint32_t filtered_goal = arm::NeutralIndex();
   if (unsafe_goal != nullptr) {
     filtered_goal = *unsafe_goal;
   }