orinoco: Fix inappropriate use of IRQ_BAP

This hardware buffer should only be used from an interrupt. The
wireless event generation functions are called from a workqueue, so use
USER_BAP instead.

Signed-off-by: David Kilroy <kilroyd@googlemail.com>
Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>