Update VmaCallbacks to return bool

A change to libmeminfo now requires that VmaCallbacks return a bool
value. This updates the existing usage in camera_device.cc with a no-op
'return true'.

Test: n/a
Bug: 320480542
Change-Id: I1f3756a3729c90a8cef2f6159109c649e7c19b52
diff --git a/common/hal/google_camera_hal/camera_device.cc b/common/hal/google_camera_hal/camera_device.cc
index 55c3a41..0520626 100644
--- a/common/hal/google_camera_hal/camera_device.cc
+++ b/common/hal/google_camera_hal/camera_device.cc
@@ -103,6 +103,7 @@
                            })) {
       ReadAheadVma(vma, kMadviseSizeLimitBytes);
     }
+    return true;
   };
   ProcMemInfo meminfo(getpid());
   meminfo.ForEachVmaFromMaps(vmaCollectorCb);