USB: opticon: Fix long-standing bugs in opticon driver

USB: opticon: Fix long-standing bugs in opticon driver

commit 97cd8dc4ca9a1a5efb2cc38758e01492e3b013e2 upstream.

The bulk-read callback had two bugs:
a) The bulk-in packet's leading two zeros were returned (and the two last
   bytes truncated)
b) The wrong URB was transmitted for the second (and later) read requests,
   causing further reads to return the entire packet (including leading
   zeros)

Signed-off-by: Alon Ziv <alon-git@nolaviz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>