zd1211rw: remove URB_SHORT_NOT_OK flag in zd_usb_iowrite16v_async()

Patch removes the bogus flag introduced by upstream commit
eefdbec1. Old code had buffer length check
that new code tried to handle with URB_SHORT_NOT_OK flag. With USB debugging
enabled bogus flag caused usb_submit_urb fail.

Remove URB_SHORT_NOT_OK flag and add buffer length check to urb completion
handler.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=32092


Reported-by: Jonathan Callen <abcd@gentoo.org>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>