iwlwifi: remove SKU from config

There's no SKU override, we always just use
it from EEPROM. As such, we can remove it
from the config and use it in hw_param only.
Since iwl_eeprom_check_sku() really needs
to fill it in also rename that to
iwl_eeprom_init_hw_params().

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>