vmm: Remove 'mergeable' from memory zones

The flag 'mergeable' should only apply to the entire guest RAM, which is
why it is removed from the MemoryZoneConfig as it is defined as a global
parameter at the MemoryConfig level.

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

vmm/src/memory_manager.rs

@@ -362,7 +362,6 @@ impl MemoryManager {
             let zones = vec![MemoryZoneConfig {
                 size: config.size,
                 file: None,
-                mergeable: config.mergeable,
                 shared: config.shared,
                 hugepages: config.hugepages,
             }];