iwlwifi: refactor init geos function

This patch refactors init geos function. It also fixes few minor bugs.
IWL_MAX_RATE -> IWL_RATE_COUNT (IWL_MAX_RATE included also MCS setting)
There are 9 and 13 rates for 4965 in 2.4 and 5.2 respectively  (rate 60)

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>