Revert "Fix widevine drm hal resource leaks"

This reverts commit 006506278a.

It needs to be reverted to fix b/38343960 on marlin.

This change is not needed since the root cause of the
resource leak was addressed in ag/2226738. 

Change-Id: I93b64d39103d574b7dcde6b1477839a50b64aefd

libwvdrmengine/mediadrm/include_hidl/WVDrmPlugin.h

@@ -38,7 +38,6 @@ using ::android::hardware::hidl_string;
 using ::android::hardware::hidl_vec;
 using ::android::hardware::Return;
 using ::android::sp;
-using ::android::wp;
 
 using android::status_t;
 using std::map;
@@ -351,7 +350,7 @@ struct WVDrmPlugin : public IDrmPlugin, IDrmPluginListener,
   sp<wvcdm::WvContentDecryptionModule> const mCDM;
   WVGenericCryptoInterface* mCrypto;
   map<CdmSessionId, CryptoSession> mCryptoSessions;
-  wp<IDrmPluginListener> mListener;
+  sp<IDrmPluginListener> mListener;
 
   status_t queryProperty(const std::string& property,
                          std::string& stringValue) const;