iwlwifi: mvm: fix WGDS table print in iwl_mvm_chub_update_mcc()

WGDS table index 0 means disabled, but we were erroneously checking
for < 0 to print that it is disabled.  Fix that and make the print
more readable by mentioning that it's either disabled or there was an
error.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20211024181719.98a5572bf0f8.I6c112ca80cf427f12b2c752899d293cb6437ba5f@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>