[media] radio-wl1273: remove unused wl1273_device->work

wl1273_device->work is unused.  Remove it along with the spurious
flush_scheduled_work() call in wl1273_fm_module_exit().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Matti Aaltonen <matti.j.aaltonen@nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>