Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/soundtrigger/ISoundTrigger.cpp b/soundtrigger/ISoundTrigger.cpp
index 4df2068..25332a4 100644
--- a/soundtrigger/ISoundTrigger.cpp
+++ b/soundtrigger/ISoundTrigger.cpp
@@ -37,7 +37,7 @@
 class BpSoundTrigger: public BpInterface<ISoundTrigger>
 {
 public:
-    BpSoundTrigger(const sp<IBinder>& impl)
+    explicit BpSoundTrigger(const sp<IBinder>& impl)
         : BpInterface<ISoundTrigger>(impl)
     {
     }
diff --git a/soundtrigger/ISoundTriggerClient.cpp b/soundtrigger/ISoundTriggerClient.cpp
index e0d3add..1385631 100644
--- a/soundtrigger/ISoundTriggerClient.cpp
+++ b/soundtrigger/ISoundTriggerClient.cpp
@@ -35,7 +35,7 @@
 {
 
 public:
-    BpSoundTriggerClient(const sp<IBinder>& impl)
+    explicit BpSoundTriggerClient(const sp<IBinder>& impl)
         : BpInterface<ISoundTriggerClient>(impl)
     {
     }
diff --git a/soundtrigger/ISoundTriggerHwService.cpp b/soundtrigger/ISoundTriggerHwService.cpp
index e37bae3..d44f5cb 100644
--- a/soundtrigger/ISoundTriggerHwService.cpp
+++ b/soundtrigger/ISoundTriggerHwService.cpp
@@ -45,7 +45,7 @@
 class BpSoundTriggerHwService: public BpInterface<ISoundTriggerHwService>
 {
 public:
-    BpSoundTriggerHwService(const sp<IBinder>& impl)
+    explicit BpSoundTriggerHwService(const sp<IBinder>& impl)
         : BpInterface<ISoundTriggerHwService>(impl)
     {
     }