SELFOUR-551: Prevent vcpu_boot_init appearing to verification
SELFOUR-551: Prevent vcpu_boot_init appearing to verification

When hypervisor extensions are not enabled the boot code cannot
actually call vcpu_boot_init as the symbol names do not even
exist. This is fixed be defining macros that expand to nothing

cmr/seL4,cmr/seL4,cmr/seL4