iwlwifi: configure uCode to use open loop tx power algorithm

This patch configures uCode to use open loop tx power algorithm
via TX_POWER_DBM (0x98) host command.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>