Allow UEFI on 32 bits machines

[frankiejol]

UEFI is only allowed on 64 bits architecture but it can be enabled for 32 bits too.

Insert these in the XML config:

• loader: /usr/share/OVMF/OVMF32_CODE_4M.fd
• nvram template='/usr/share/OVMF/OVMF32_VARS_4M.fd'

Enable UEFI and Legacy selection on frontend new machine.