samples: rust: pci: 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>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20251222-cstr-pci-v1-1-a0397c61bbe4@gmail.com
[ Use kernel vertical import style. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

samples/rust/rust_driver_pci.rs

@@ -4,7 +4,13 @@
 //!
 //! To make this driver probe, QEMU must be run with `-device pci-testdev`.
 
-use kernel::{c_str, device::Core, devres::Devres, pci, prelude::*, sync::aref::ARef};
+use kernel::{
+    device::Core,
+    devres::Devres,
+    pci,
+    prelude::*,
+    sync::aref::ARef, //
+};
 
 struct Regs;
 
@@ -79,7 +85,7 @@ impl pci::Driver for SampleDriver {
             pdev.set_master();
 
             Ok(try_pin_init!(Self {
-                bar <- pdev.iomap_region_sized::<{ Regs::END }>(0, c_str!("rust_driver_pci")),
+                bar <- pdev.iomap_region_sized::<{ Regs::END }>(0, c"rust_driver_pci"),
                 index: *info,
                 _: {
                     let bar = bar.access(pdev.as_ref())?;