rust: drm: use core::ffi::CStr method names

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: #1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: tamird

rust/kernel/drm/device.rs

@@ -82,8 +82,8 @@ impl<T: drm::Driver> Device<T> {
         major: T::INFO.major,
         minor: T::INFO.minor,
         patchlevel: T::INFO.patchlevel,
-        name: T::INFO.name.as_char_ptr().cast_mut(),
-        desc: T::INFO.desc.as_char_ptr().cast_mut(),
+        name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
+        desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),
 
         driver_features: drm::driver::FEAT_GEM,
         ioctls: T::IOCTLS.as_ptr(),