Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I0ce850de85e0de6a5472dd142f738856142db9ec
diff --git a/libs/gui/ISensorServer.cpp b/libs/gui/ISensorServer.cpp
index f581b5c..b0ba134 100644
--- a/libs/gui/ISensorServer.cpp
+++ b/libs/gui/ISensorServer.cpp
@@ -41,7 +41,7 @@
 class BpSensorServer : public BpInterface<ISensorServer>
 {
 public:
-    BpSensorServer(const sp<IBinder>& impl)
+    explicit BpSensorServer(const sp<IBinder>& impl)
         : BpInterface<ISensorServer>(impl)
     {
     }