Remove orphaned source files which are never used

Remove vmm_config/console.rs file whis is never used (there is no corresponding
`mod console`) and device_manager/mmio.rs which has been split into 2 versions:
device_manager/kvm/mmio.rs and device_manager/hvf/mmio.rs

Signed-off-by: Matej Hrica <mhrica@redhat.com>

Author: mtjhrc