iwlwifi: pass the iwl_trans instead of cfg to some functions

A few functions were receiving the iwl_cfg struct directly, but we
will also need other parts of the trans, so pass the trans (which
includes the cfg) to them.

Signed-off-by: Ido Yariv <idox.yariv@intel.com>
Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>