I am planning to use MaaS for my deployment automation of workloads on bare metal servers. One of the prerequisite is to enable SR-IOV in BIOS. The server is DELL rack server. Can I add this into the automation steps using MAAS?
Nope: you cannot configure the BIOS/UEFI of the machines though MAAS.
Some vendors deliver some software to be installed on the machine that let you change the bios/uefi settings, but this is something you have to run on your own after you have deployed a machine with MAAS.
Also, see the reply from @troyanov on a similar question How to set BIOS setting of target server in MaaS