Add a second thread for sensor service.

HIDL implementation defaults to using a single thread for a service.
This blocks on sensorservice poll. A minimum of two threads are needed
to allow for any meaningful control.

Bug: 35067266
Test: Verify sensors stream in both passthrough and binderized modes.
Change-Id: I44ccdb6db253ca9eb9903b51e05c1893945e297e
diff --git a/sensors/1.0/default/service.cpp b/sensors/1.0/default/service.cpp
index 5bcfe4b..65f6d81 100644
--- a/sensors/1.0/default/service.cpp
+++ b/sensors/1.0/default/service.cpp
@@ -23,5 +23,9 @@
 using android::hardware::defaultPassthroughServiceImplementation;
 
 int main() {
-    return defaultPassthroughServiceImplementation<ISensors>();
+    /* Sensors framework service needs at least two threads.
+     * One thread blocks on a "poll"
+     * The second thread is needed for all other HAL methods.
+     */
+    return defaultPassthroughServiceImplementation<ISensors>(2);
 }