MTP: Write initial data to correct file offset in SendPartialObject

Change-Id: I84288aeda3e65e6e6487f11d32a72910cd16cff2
diff --git a/media/mtp/MtpServer.cpp b/media/mtp/MtpServer.cpp
index 662a93d..8568dfc 100644
--- a/media/mtp/MtpServer.cpp
+++ b/media/mtp/MtpServer.cpp
@@ -1118,7 +1118,7 @@
     int initialData = ret - MTP_CONTAINER_HEADER_SIZE;
 
     if (initialData > 0) {
-        ret = write(edit->mFD, mData.getData(), initialData);
+        ret = pwrite(edit->mFD, mData.getData(), initialData, offset);
         offset += initialData;
         length -= initialData;
     }