Add -webcam commandline option to control webcam emulation

-webcam name=<name>[,dir=<direction>] options controls web cameras to use for emulation.

Change-Id: I961fd399c7e041541adda040dd24f194cc383cb9
diff --git a/vl-android.c b/vl-android.c
index f657258..f0b2ae8 100644
--- a/vl-android.c
+++ b/vl-android.c
@@ -2619,7 +2619,6 @@
     boot_property_init_service();
     android_hw_control_init();
     android_net_pipes_init();
-    android_camera_service_init();
 
 #ifdef CONFIG_KVM
     /* By default, force auto-detection for kvm */
@@ -3468,6 +3467,11 @@
             case QEMU_OPTION_snapshot_no_time_update:
                 android_snapshot_update_time = 0;
                 break;
+
+            case QEMU_OPTION_list_webcam:
+                android_list_web_cameras();
+                exit(0);
+
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }
@@ -3741,6 +3745,9 @@
         boot_property_add("qemu.sf.fake_camera", "back");
     }
 
+    /* Initialize camera emulation. */
+    android_camera_service_init();
+
     if (android_op_cpu_delay) {
         char*   end;
         long    delay = strtol(android_op_cpu_delay, &end, 0);