Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/camera/ICamera.cpp b/camera/ICamera.cpp
index 9943be6..93f8342 100644
--- a/camera/ICamera.cpp
+++ b/camera/ICamera.cpp
@@ -54,7 +54,7 @@
 class BpCamera: public BpInterface<ICamera>
 {
 public:
-    BpCamera(const sp<IBinder>& impl)
+    explicit BpCamera(const sp<IBinder>& impl)
         : BpInterface<ICamera>(impl)
     {
     }