Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/camera/ICameraServiceProxy.cpp b/camera/ICameraServiceProxy.cpp
index 694e9c3..a9d0836 100644
--- a/camera/ICameraServiceProxy.cpp
+++ b/camera/ICameraServiceProxy.cpp
@@ -26,7 +26,8 @@
 
 class BpCameraServiceProxy: public BpInterface<ICameraServiceProxy> {
 public:
-    BpCameraServiceProxy(const sp<IBinder>& impl) : BpInterface<ICameraServiceProxy>(impl) {}
+    explicit BpCameraServiceProxy(const sp<IBinder>& impl)
+        : BpInterface<ICameraServiceProxy>(impl) {}
 
     virtual void pingForUserUpdate() {
         Parcel data;