Testing: KVM support

[ricardosalveti]

Boot firmware files from the 1.3 release includes xbl_config_kvm.elf which can be used to enable KVM support at runtime.

Just replace xbl_config.elf with xbl_config_kvm.elf and should be enough for KVM to be available (gunyah won't be available, and could cause other runtime issues with dsp firmware verification, but that is outside the scope of this ask).