iwlwifi: Don't IWL_WARN on FW reconfiguration

iwlwifi: Don't IWL_WARN on FW reconfiguration

IWL_WARN seems excessive here since this can happen during normal
operation. Every time I connect to a new network with 8086:24fd I get
this as KERN_WARNING on the console, which mildly distracts from other
more pressing messages. For example:

    % sudo journalctl _TRANSPORT=kernel | grep -c 'FW already configured'
    403

Signed-off-by: Chris Down <chris@chrisdown.name>
Cc: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Cc: Luca Coelho <luciano.coelho@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Link: https://lore.kernel.org/r/20191017144841.GA16393@chrisdown.name
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>