Hello HC,
Thank you for posting your question on the NVIDIA/Mellanox Community.
The message you are getting is a harmless message from the kernel itself and can be ignored. You can resolve this by following the instructions on how-to Enroll Mellanox’s x.509 Public Key On your Systems → https://docs.mellanox.com/display/OFEDv502180/UEFI+Secure+Boot#UEFISecureBoot-RemovingSignaturefromKernelModules
Note: even if you strip the module if his signature, you will still see this harmless message.
Thank you,
~NVIDIA/Mellanox Technical Support