The transfer buffer of an URB will be automatically freed when using
the URB_FREE_BUFFER transfer_flag. So the extra calls to kfree() will
cause a double free.

Reported-by: Justin Mattock <justinmattock@gmail.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>