rust: error: import kernel's LayoutError instead of core's

Import the internal (`kernel::alloc`) version of `LayoutError` instead
of the `core::alloc` one.

In particular, this results in switching the type in the existing
`From<LayoutError> for Error` implementation.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Jimmy Ostler <jtostler1@gmail.com>
Link: https://lore.kernel.org/r/fe58a02189e8804a9eabdd01cb1927d4c491d79c.1734674670.git.jtostler1@gmail.com
[ Reworded commit. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: LordGoatius

rust/kernel/error.rs

@@ -4,9 +4,10 @@
 //!
 //! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)
 
-use crate::{alloc::AllocError, str::CStr};
-
-use core::alloc::LayoutError;
+use crate::{
+    alloc::{layout::LayoutError, AllocError},
+    str::CStr,
+};
 
 use core::fmt;
 use core::num::NonZeroI32;