usb: misc: usbtest: fix pattern tests for scatterlists.

The current implemenentation restart the sent pattern for each entry in
the sg list. The receiving end expects a continuous pattern, and test
will fail unless scatterilst entries happen to be aligned with the
pattern

Fix this by calculating the pattern byte based on total sent size
instead of just the current sg entry.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Fixes: 8b524901 ("[PATCH] USB: usbtest: scatterlist OUT data pattern testing")
Cc: <stable@vger.kernel.org> # v2.6.18+
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>