[PATCH] ipw2200: use jiffies_to_msec() wherever possible

This substitutes Linux jiffies_to_msec() wherever there is a
computation for determining milliseconds from jiffies,
following lead from ieee80211 code. And it does a little cleanup.
"it's" == "it is" ... "its" == possessive "it". Indulge me. ;-)

Signed-off-by: Cahill, Ben M <ben.m.cahill@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>