iwl3945: rearrange the code.

Rearrange the code and groups setting of
retry_limit and data_retry_limits code together.
Make 'data_retry_limit' setting similar to iwlwifi
for better readability.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>