iwlwifi: mvm: always init rs_fw with 20MHz bandwidth rates

As with the non-offloaded rs case, during assoc on the ap side the phy
context is set to 20MHz until authorization of a client that supports
wider channel-widths. Support this by sending the initial
tlc_config_cmd with max supported channel width of 20MHz until
authorization succeeds.

Fixes: 6b7a5aea ("iwlwifi: mvm: always init rs with 20mhz bandwidth rates")
Signed-off-by: Naftali Goldstein <naftali.goldstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>