rust: regulator: 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.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Daniel Almeida <Daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20251222-cstr-regulator-v1-1-430e3d517025@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: tamird

rust/kernel/regulator.rs

@@ -122,12 +122,11 @@ pub fn devm_enable_optional(dev: &Device<Bound>, name: &CStr) -> Result {
 ///
 /// ```
 /// # use kernel::prelude::*;
-/// # use kernel::c_str;
 /// # use kernel::device::Device;
 /// # use kernel::regulator::{Voltage, Regulator, Disabled, Enabled};
 /// fn enable(dev: &Device, min_voltage: Voltage, max_voltage: Voltage) -> Result {
 ///     // Obtain a reference to a (fictitious) regulator.
-///     let regulator: Regulator<Disabled> = Regulator::<Disabled>::get(dev, c_str!("vcc"))?;
+///     let regulator: Regulator<Disabled> = Regulator::<Disabled>::get(dev, c"vcc")?;
 ///
 ///     // The voltage can be set before enabling the regulator if needed, e.g.:
 ///     regulator.set_voltage(min_voltage, max_voltage)?;
@@ -166,12 +165,11 @@ pub fn devm_enable_optional(dev: &Device<Bound>, name: &CStr) -> Result {
 ///
 /// ```
 /// # use kernel::prelude::*;
-/// # use kernel::c_str;
 /// # use kernel::device::Device;
 /// # use kernel::regulator::{Voltage, Regulator, Enabled};
 /// fn enable(dev: &Device) -> Result {
 ///     // Obtain a reference to a (fictitious) regulator and enable it.
-///     let regulator: Regulator<Enabled> = Regulator::<Enabled>::get(dev, c_str!("vcc"))?;
+///     let regulator: Regulator<Enabled> = Regulator::<Enabled>::get(dev, c"vcc")?;
 ///
 ///     // Dropping an enabled regulator will disable it. The refcount will be
 ///     // decremented.
@@ -193,13 +191,12 @@ pub fn devm_enable_optional(dev: &Device<Bound>, name: &CStr) -> Result {
 ///
 /// ```
 /// # use kernel::prelude::*;
-/// # use kernel::c_str;
 /// # use kernel::device::{Bound, Device};
 /// # use kernel::regulator;
 /// fn enable(dev: &Device<Bound>) -> Result {
 ///     // Obtain a reference to a (fictitious) regulator and enable it. This
 ///     // call only returns whether the operation succeeded.
-///     regulator::devm_enable(dev, c_str!("vcc"))?;
+///     regulator::devm_enable(dev, c"vcc")?;
 ///
 ///     // The regulator will be disabled and put when `dev` is unbound.
 ///     Ok(())