rust: clk: replace kernel::c_str! with C-Strings

C-String literals were added in Rust 1.77. Replace instances of
`kernel::c_str!` with C-String literals where possible.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20251222-cstr-clk-v1-1-ef0687717aa1@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: tamird

rust/kernel/clk.rs

@@ -104,13 +104,12 @@ mod common_clk {
     /// The following example demonstrates how to obtain and configure a clock for a device.
     ///
     /// ```
-    /// use kernel::c_str;
     /// use kernel::clk::{Clk, Hertz};
     /// use kernel::device::Device;
     /// use kernel::error::Result;
     ///
     /// fn configure_clk(dev: &Device) -> Result {
-    ///     let clk = Clk::get(dev, Some(c_str!("apb_clk")))?;
+    ///     let clk = Clk::get(dev, Some(c"apb_clk"))?;
     ///
     ///     clk.prepare_enable()?;
     ///
@@ -272,13 +271,12 @@ mod common_clk {
     /// device. The code functions correctly whether or not the clock is available.
     ///
     /// ```
-    /// use kernel::c_str;
     /// use kernel::clk::{OptionalClk, Hertz};
     /// use kernel::device::Device;
     /// use kernel::error::Result;
     ///
     /// fn configure_clk(dev: &Device) -> Result {
-    ///     let clk = OptionalClk::get(dev, Some(c_str!("apb_clk")))?;
+    ///     let clk = OptionalClk::get(dev, Some(c"apb_clk"))?;
     ///
     ///     clk.prepare_enable()?;
     ///