iwl3945: place CCK rates in front of OFDM for supported rates

The patch fixes association failure (reason = 18) bug by arranging CCK
rates before OFDM rates. This patch will register with mac80211 the
modified rate arrangement with CCK rate first. Change rate scale algorithm
also to deal with rate change. Fix Txpower and rate Table commands to be
constructed correctly after rearrangement.

Signed-off-by: Mohamed Abbas <mabbas@linux.intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>