Change v4l2_wrapper set control to accept null.

User does not need to pass a result pointer if they
don't care about the result.

BUG: 30140438

Change-Id: Ia98870f24df82464a3f00aad63a599063b98f03a
diff --git a/modules/camera/3_4/v4l2_wrapper.h b/modules/camera/3_4/v4l2_wrapper.h
index d67b36e..113499a 100644
--- a/modules/camera/3_4/v4l2_wrapper.h
+++ b/modules/camera/3_4/v4l2_wrapper.h
@@ -45,7 +45,8 @@
   // Manage controls.
   int QueryControl(uint32_t control_id, v4l2_query_ext_ctrl* result);
   int GetControl(uint32_t control_id, int32_t* value);
-  int SetControl(uint32_t control_id, int32_t desired, int32_t* result);
+  int SetControl(uint32_t control_id, int32_t desired,
+                 int32_t* result = nullptr);
   // Manage format.
   int SetFormat(const default_camera_hal::Stream& stream,
                 uint32_t* result_max_buffers);