We were assigning the return value of iwl_mvm_ctdp_command() to a
variable, but never checking it. If this command fails, we should not
allow the interface up process to proceed, since it is potentially
dangerous to ignore thermal management requirements.
Fixes: commit 5c89e7bc55 ("iwlwifi: mvm: add registration to cooling device")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>