iwlwifi: mvm: don't send CTDP commands via debugfs if not supported

Fix this issue if it is not supported by the firmware.

Fixes: 00f481bd ("iwlwifi: mvm: add ctdp operations to debugfs")
Signed-off-by: Matt Chen <matt.chen@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>