rust: alloc: make allocator module public

Subsequent patches implement allocators such as `Kmalloc`, `Vmalloc`,
`KVmalloc`; we need them to be available outside of the kernel crate as
well.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241004154149.93856-6-dakr@kernel.org

Author: Danilo Krummrich

rust/kernel/alloc.rs

@@ -4,7 +4,7 @@
 
 #[cfg(not(test))]
 #[cfg(not(testlib))]
-mod allocator;
+pub mod allocator;
 pub mod box_ext;
 pub mod vec_ext;