[PATCH v2] rust: cpufreq: Add CPUFREQ_TABLE_END as last table entry in TableBuilder::to_table

The `TableBuilder::to_table` function adds `Hertz(c_ulong::MAX).as_khz()`
as the last frequency entry in the frequency table.
But the C API expects the last entry to have frequency set to
`CPUFREQ_TABLE_END` which is `~1u` as per include/linux/cpufreq.h.

Fix this by setting the last frequency entry to `CPUFREQ_TABLE_END`
instead of `Hertz(c_ulong::MAX).as_khz()`.

Fixes: 2207856ff0bc8d953d6e89bda70b8978c2de8bab ("rust: cpufreq: Add initial abstractions for cpufreq framework")
Reported-by: Dylan Zueck<[email protected]>
Reported-by: Yuan Tan<[email protected]>
Assisted-by: ChatGPT:gpt-5.6-terra
Signed-off-by: Priya Bala Govindasamy<[email protected]>

Changes in v2:
 - Create `TableBuilder::push` method to add entries to the table
   without converting the frequency to kHz.
 - `TableBuilder::add` now internally uses `TableBuilder::push` to add
   entries to the table after converting the frequency to kHz.
 - Use the new `TableBuilder::push` method to add to the last table
   entry.
 - Link to v1: https://lore.kernel.org/rust-for-linux/[email protected]/T/#t
---
 rust/kernel/cpufreq.rs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index 58ac04c650a1..f360eb9578f3 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -361,23 +361,28 @@ pub fn new() -> Self {
         }
     }
 
-    /// Adds a new entry to the table.
-    pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result {
+    /// Adds a raw frequency-table entry.
+    fn push(&mut self, frequency: u32, flags: u32, driver_data: u32) -> Result {
         // Adds the new entry at the end of the vector.
         Ok(self.entries.push(
             bindings::cpufreq_frequency_table {
                 flags,
                 driver_data,
-                frequency: freq.as_khz() as u32,
+                frequency,
             },
             GFP_KERNEL,
         )?)
     }
 
+    /// Adds a new entry to the table.
+    pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result {
+        self.push(freq.as_khz() as u32, flags, driver_data)
+    }
+
     /// Consumes the [`TableBuilder`] and returns [`TableBox`].
     pub fn to_table(mut self) -> Result<TableBox> {
         // Add last entry to the table.
-        self.add(Hertz(c_ulong::MAX), 0, 0)?;
+        self.push(bindings::CPUFREQ_TABLE_END as u32, 0, 0)?;
 
         TableBox::new(self.entries)
     }
-- 
2.34.1