refactor(virtio-mem): use u64_to_usize instead of try_into+unwrap

It's better to be explicit on the conversion we're doing as u64 to usize
is always safe in our platforms.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

src/vmm/src/devices/virtio/mem/device.rs

@@ -125,12 +125,12 @@ impl VirtioMem {
 
     /// Gets the total hotpluggable size.
     pub fn total_size_mib(&self) -> usize {
-        bytes_to_mib(self.config.region_size.try_into().unwrap())
+        bytes_to_mib(u64_to_usize(self.config.region_size))
     }
 
     /// Gets the block size.
     pub fn block_size_mib(&self) -> usize {
-        bytes_to_mib(self.config.block_size.try_into().unwrap())
+        bytes_to_mib(u64_to_usize(self.config.block_size))
     }
 
     /// Gets the block size.
@@ -140,12 +140,12 @@ impl VirtioMem {
 
     /// Gets the total size of the plugged memory blocks.
     pub fn plugged_size_mib(&self) -> usize {
-        bytes_to_mib(self.config.plugged_size.try_into().unwrap())
+        bytes_to_mib(u64_to_usize(self.config.plugged_size))
     }
 
     /// Gets the requested size
     pub fn requested_size_mib(&self) -> usize {
-        bytes_to_mib(self.config.requested_size.try_into().unwrap())
+        bytes_to_mib(u64_to_usize(self.config.requested_size))
     }
 
     pub fn status(&self) -> VirtioMemStatus {