ipw2100: fix timeout bug - always evaluated to 0

commit 2c86c275 ("Add ipw2100 wireless driver.") introduced
HW_PHY_OFF_LOOP_DELAY (HZ / 5000) which always evaluated to 0. Clarified
by Stanislav Yakovlev <stas.yakovlev@gmail.com> that it should be 50
milliseconds thus fixed up to msecs_to_jiffies(50).

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Acked-by: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>