rust: regulator: use CStr::as_char_ptr

Replace the use of `as_ptr` which works through `<CStr as
Deref<Target=&[u8]>::deref()` in preparation for replacing
`kernel::str::CStr` with `core::ffi::CStr` as the latter does not
implement `Deref<Target=&[u8]>`.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20251018-cstr-core-v18-13-9378a54385f8@gmail.com
[ Move safety comment below to support older Clippy. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: tamird

rust/kernel/regulator.rs

@@ -84,7 +84,7 @@ pub struct Error<State: RegulatorState> {
 pub fn devm_enable(dev: &Device<Bound>, name: &CStr) -> Result {
     // SAFETY: `dev` is a valid and bound device, while `name` is a valid C
     // string.
-    to_result(unsafe { bindings::devm_regulator_get_enable(dev.as_raw(), name.as_ptr()) })
+    to_result(unsafe { bindings::devm_regulator_get_enable(dev.as_raw(), name.as_char_ptr()) })
 }
 
 /// Same as [`devm_enable`], but calls `devm_regulator_get_enable_optional`
@@ -102,7 +102,9 @@ pub fn devm_enable(dev: &Device<Bound>, name: &CStr) -> Result {
 pub fn devm_enable_optional(dev: &Device<Bound>, name: &CStr) -> Result {
     // SAFETY: `dev` is a valid and bound device, while `name` is a valid C
     // string.
-    to_result(unsafe { bindings::devm_regulator_get_enable_optional(dev.as_raw(), name.as_ptr()) })
+    to_result(unsafe {
+        bindings::devm_regulator_get_enable_optional(dev.as_raw(), name.as_char_ptr())
+    })
 }
 
 /// A `struct regulator` abstraction.
@@ -266,9 +268,10 @@ impl<T: RegulatorState> Regulator<T> {
     }
 
     fn get_internal(dev: &Device, name: &CStr) -> Result<Regulator<T>> {
-        // SAFETY: It is safe to call `regulator_get()`, on a device pointer
-        // received from the C code.
-        let inner = from_err_ptr(unsafe { bindings::regulator_get(dev.as_raw(), name.as_ptr()) })?;
+        let inner =
+            // SAFETY: It is safe to call `regulator_get()`, on a device pointer
+            // received from the C code.
+            from_err_ptr(unsafe { bindings::regulator_get(dev.as_raw(), name.as_char_ptr()) })?;
 
         // SAFETY: We can safely trust `inner` to be a pointer to a valid
         // regulator if `ERR_PTR` was not returned.