fastbootd: Fix USB transport data is repeated every 256K

When Write() is called on data > 256K, the written data
repeats every 256K because of the buggy line in this change.

Test: fastboot fetch vendor_boot.img
Fixes: 180654366

Change-Id: I33b129de27000d3f32f284469998daf540d4f856
diff --git a/fastboot/device/usb_client.cpp b/fastboot/device/usb_client.cpp
index 2caced4..3f9b0f0 100644
--- a/fastboot/device/usb_client.cpp
+++ b/fastboot/device/usb_client.cpp
@@ -283,7 +283,7 @@
     size_t bytes_written_total = 0;
     while (bytes_written_total < len) {
         auto bytes_to_write = std::min(len - bytes_written_total, kFbFfsNumBufs * kFbFfsBufSize);
-        auto bytes_written_now = handle_->write(handle_.get(), data, bytes_to_write);
+        auto bytes_written_now = handle_->write(handle_.get(), char_data, bytes_to_write);
         if (bytes_written_now < 0) {
             return bytes_written_total == 0 ? -1 : bytes_written_total;
         }