vmm: Move SerialBuffer to its own crate

We want to be able to reuse the SerialBuffer from the virtio-devices
crate, particularly from the virtio-console implementation. That's why
we move the SerialBuffer definition to its own crate so that it can be
accessed from both vmm and virtio-devices crates, without creating any
cyclic dependency.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/lib.rs

@@ -70,7 +70,6 @@ pub mod memory_manager;
 pub mod migration;
 mod pci_segment;
 pub mod seccomp_filters;
-mod serial_buffer;
 mod serial_manager;
 mod sigwinch_listener;
 pub mod vm;