Fix gralloc direct channel bug and polish log messages

1) Remove obsoleted stub code so that second gralloc direct channel
   can be successfully registered.

2) Remove obsoleted misleading log messages.
3) Add missing log messages at failure to help debugging.

Bug: 36900495
Test: SensorDirectReportTest
Change-Id: I1d6941c4179338f6db8f84079844dce515b80516
diff --git a/services/sensorservice/SensorDirectConnection.cpp b/services/sensorservice/SensorDirectConnection.cpp
index b096e1c..91923b3 100644
--- a/services/sensorservice/SensorDirectConnection.cpp
+++ b/services/sensorservice/SensorDirectConnection.cpp
@@ -185,17 +185,18 @@
                 struct stat s1, s2;
                 int fd1, fd2;
                 fd1 = mMem.handle->data[0];
-                fd2 = mem->handle->data[1];
+                fd2 = mem->handle->data[0];
                 if (fstat(fd1, &s1) < 0 || fstat(fd2, &s2) < 0 || s1.st_ino == s2.st_ino) {
                     ret = true;
                 }
                 break;
             }
             case SENSOR_DIRECT_MEM_TYPE_GRALLOC:
-                LOG_FATAL("%s: Implement GRALLOC or remove", __FUNCTION__);
-                ret = true;
+                // there is no known method to test if two gralloc handle are equivalent
+                ret = false;
                 break;
             default:
+                // should never happen
                 ALOGE("Unexpected mem type %d", mMem.type);
                 ret = true;
                 break;