media: use size_t for integer iterator to Vector::size()

Change-Id: I0a744dc7815a86a993df9b0623440be620ec8903
diff --git a/media/mtp/MtpServer.cpp b/media/mtp/MtpServer.cpp
index 0b1f527..155f645 100644
--- a/media/mtp/MtpServer.cpp
+++ b/media/mtp/MtpServer.cpp
@@ -125,7 +125,7 @@
 void MtpServer::removeStorage(MtpStorage* storage) {
     Mutex::Autolock autoLock(mMutex);
 
-    for (unsigned int i = 0; i < mStorages.size(); i++) {
+    for (size_t i = 0; i < mStorages.size(); i++) {
         if (mStorages[i] == storage) {
             mStorages.removeAt(i);
             sendStoreRemoved(storage->getStorageID());
@@ -137,7 +137,7 @@
 MtpStorage* MtpServer::getStorage(MtpStorageID id) {
     if (id == 0)
         return mStorages[0];
-    for (unsigned int i = 0; i < mStorages.size(); i++) {
+    for (size_t i = 0; i < mStorages.size(); i++) {
         MtpStorage* storage = mStorages[i];
         if (storage->getStorageID() == id)
             return storage;