Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I0ce850de85e0de6a5472dd142f738856142db9ec
diff --git a/libs/binder/IProcessInfoService.cpp b/libs/binder/IProcessInfoService.cpp
index d86eb27..794588b 100644
--- a/libs/binder/IProcessInfoService.cpp
+++ b/libs/binder/IProcessInfoService.cpp
@@ -25,7 +25,7 @@
 
 class BpProcessInfoService : public BpInterface<IProcessInfoService> {
 public:
-    BpProcessInfoService(const sp<IBinder>& impl)
+    explicit BpProcessInfoService(const sp<IBinder>& impl)
         : BpInterface<IProcessInfoService>(impl) {}
 
     virtual status_t getProcessStatesFromPids(size_t length, /*in*/ int32_t* pids,