iwlwifi: Add chain_noise support for 6050

Existing iwl6050_ops->iwl6050_hcmd_utils structure had no pointers to chain
noise functions (gain_computation and chain_noise_reset).  As it turns out,
by adding chain_noise_scale (see related patch), there is no need for separate
chain noise function, so simply use iwl6000_ops->iwl5000_hcmd_utils, and
remove those for 6050.

Signed-off-by: Ben Cahill <ben.m.cahill@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>