rust: use checked_div to make clippy happy

When upgrading from Fedora 41 to Fedora 43 for CI tests, clippy begins
complaining about not using checked_div instead of manually checking
divisors. Make clippy happy and use checked_div() instead.

Signed-off-by: John Snow <jsnow@redhat.com>
Link: https://lore.kernel.org/r/20260219185409.708130-2-jsnow@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/Cargo.toml

@@ -46,6 +46,7 @@ redundant_explicit_links = "deny"
 [workspace.lints.clippy]
 # default-warn lints
 result_unit_err = "allow"
+manual_checked_ops = "deny"
 should_implement_trait = "deny"
 # can be for a reason, e.g. in callbacks
 unused_self = "allow"

rust/hw/core/src/qdev.rs

@@ -425,18 +425,16 @@ impl Clock {
     }
 
     pub const fn period_from_hz(hz: u64) -> u64 {
-        if hz == 0 {
-            0
-        } else {
-            Self::PERIOD_1SEC / hz
+        match Self::PERIOD_1SEC.checked_div(hz) {
+            Some(value) => value,
+            None => 0,
         }
     }
 
     pub const fn period_to_hz(period: u64) -> u64 {
-        if period == 0 {
-            0
-        } else {
-            Self::PERIOD_1SEC / period
+        match Self::PERIOD_1SEC.checked_div(period) {
+            Some(value) => value,
+            None => 0,
         }
     }