misc: Fix beta clippy errors

Fix clippy error: "error: manual implementation of `.is_multiple_of()
`" from rustc 1.90.0-beta.1 (788da80fc 2025-08-04).

Signed-off-by: Songqian Li <sionli@tencent.com>

vmm/src/memory_manager.rs

@@ -1700,7 +1700,7 @@ impl MemoryManager {
         }
 
         // "Inserted" DIMM must have a size that is a multiple of 128MiB
-        if size % (128 << 20) != 0 {
+        if !size.is_multiple_of(128 << 20) {
             return Err(Error::InvalidSize);
         }