Fix/suppress libs/gui google-explicit-constructor warnings

* Add explicit to conversion constructors/operators

Bug: 28341362
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,google-explicit-constructor
Change-Id: I76384db26fac6da2de3dbb9092c26c4979324948
diff --git a/libs/gui/IGraphicBufferProducer.cpp b/libs/gui/IGraphicBufferProducer.cpp
index 0b37960..74ab5ac 100644
--- a/libs/gui/IGraphicBufferProducer.cpp
+++ b/libs/gui/IGraphicBufferProducer.cpp
@@ -536,7 +536,7 @@
 class HpGraphicBufferProducer : public HpInterface<
         BpGraphicBufferProducer, H2BGraphicBufferProducer> {
 public:
-    HpGraphicBufferProducer(const sp<IBinder>& base) : PBase(base) {}
+    explicit HpGraphicBufferProducer(const sp<IBinder>& base) : PBase(base) {}
 
     status_t requestBuffer(int slot, sp<GraphicBuffer>* buf) override {
         return mBase->requestBuffer(slot, buf);