Name big motor controller files appropriately

These won't be shared with fet12, little, or any future motor
controllers, so give them unique names.

Change-Id: I9e1cadea16792e676744f4fd39d68bbf82ed15b5
diff --git a/motors/python/BUILD b/motors/python/BUILD
index 299f4d2..408f3cd 100644
--- a/motors/python/BUILD
+++ b/motors/python/BUILD
@@ -1,7 +1,7 @@
 py_binary(
-    name = "phase_current",
+    name = "big_phase_current",
     srcs = [
-        "phase_current.py",
+        "big_phase_current.py",
     ],
     restricted_to = ["//tools:k8"],
     deps = [