Support UEFI-Preferred boot mode on AWS FortiGate-VM models

When deployed on instance types that support --boot-mode uefi-preferred, FortiGate-VM on AWS supports UEFI-Preferred boot mode. You can label AMI images as UEFI-Preferred and boot with UEFI when the instance type supports UEFI.

You can register a FortiGate-VM64-AWS custom image with the --boot-mode uefi-preferred option.

If the instance type only supports legacy BIOS boot mode, the FortiGate-VM64-AWS boots in BIOS mode even if it is labelled as --boot-mode uefi-preferred. For example, the t2.small instance type does not support UEFI-Preferred boot mode.

If the instance type supports legacy BIOS and UEFI boot modes, the FortiGate-VM64-AWS boots in UEFI mode if it is labelled as --boot-mode uefi-preferred. For example, the c6a.large instance type supports legacy BIOS and UEFI boot modes.