iwlwifi: add iwl_nic_ops structure to iwl_ops

iwlwifi: add iwl_nic_ops structure to iwl_ops

iwlwifi driver supports multiple devices. Since some device needs
special configuration we create a new iwl_nic_ops structure which is
configurable per device. Currently there is only one function pointer
inside this structure: additional_nic_config().

The iwl_nic_ops structure is added to the top level in struct iwl_ops,
making it easier to change per device. Duplication of the iwl_lib_ops
structure is no longer needed.

With this new ops the previous function pointer set_calib_version is
no longer needed since it is just a per device nic configuration.

As part of the code restructuring, a bug is addressed. Indication of
calib version to uCode is only needed for 6050 devices, however,
current implementation set calib version for all 6000 devices for
which DC calib is needed. To fix this, create iwl6050_ops for 6050
devices and only populate iwl_nic_ops in this structure.

Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>