fix uninitialized warning.

This fixes warning: The left operand of '%' is a garbage value.

Bug: None.
Test: The warning is gone.
Change-Id: I191e5bfd9d5f5136afcc2b5d8277c44b7d223998
diff --git a/media/mtp/MtpFfsHandle.cpp b/media/mtp/MtpFfsHandle.cpp
index 6c7ffcb..58d2bb8 100644
--- a/media/mtp/MtpFfsHandle.cpp
+++ b/media/mtp/MtpFfsHandle.cpp
@@ -641,6 +641,7 @@
     if (file_length == static_cast<unsigned>(init_read_len)) return 0;
     file_length -= init_read_len;
     offset += init_read_len;
+    ret = 0;
 
     // Break down the file into pieces that fit in buffers
     while(file_length > 0) {