According to VMware KB: Methods for upgrading to ESXi 5.5 upgrading (meaning upgrade "in place" using CD/DVD/USB or upgrade via VUM) from ESXi 5.1 to ESXi 5.5 does maintain custom VIBs, so you may be in luck and the driver may be "migrated" during the upgrade such that you don't have to install it again.
Just in case the driver isn't kept or you decide to reinstall rather than upgrade in place, there are a few options you can look into to determine how to proceed with the ESXi 5.5 reinstall.
Good luck! Please let us know how it goes.