[PATCH] zd1211rw: usb_clear_halt not allowed in IRQ context

We will reimplement halt-clearing later, when we have periodic
housekeeping routines in place. This will do as a temporary fix, the
EPIPE case has not yet been seen.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>