Use String8/16 c_str [audio]

Bug: 295394788
Test: make checkbuild
Change-Id: Idd3610f6820093bd8710a401f87a136cc26279c5
diff --git a/services/audioflinger/DeviceEffectManager.cpp b/services/audioflinger/DeviceEffectManager.cpp
index 681ec5f..588616d 100644
--- a/services/audioflinger/DeviceEffectManager.cpp
+++ b/services/audioflinger/DeviceEffectManager.cpp
@@ -206,17 +206,17 @@
     const bool locked = afutils::dumpTryLock(mLock);
     if (!locked) {
         String8 result("DeviceEffectManager may be deadlocked\n");
-        write(fd, result.string(), result.size());
+        write(fd, result.c_str(), result.size());
     }
 
     String8 heading("\nDevice Effects:\n");
-    write(fd, heading.string(), heading.size());
+    write(fd, heading.c_str(), heading.size());
     for (const auto& iter : mDeviceEffects) {
         String8 outStr;
         outStr.appendFormat("%*sEffect for device %s address %s:\n", 2, "",
                 ::android::toString(iter.first.mType).c_str(), iter.first.getAddress());
         for (const auto& effect : iter.second) {
-            write(fd, outStr.string(), outStr.size());
+            write(fd, outStr.c_str(), outStr.size());
             effect->dump2(fd, 4);
         }
     }