modules: optional: Bring in release fixes for Rust

This update fixes a few things that are breaking CI:

- Rust 1.85 changes the type of `core::ffi::c_char` to match the native
  platform. On some platforms, this causes a compile error in printk.  Fix
  this by using the `c_char` type directly instead of assuming it is either
  signed or unsigned

- Disable RiscV SMP targest in the samples and tests.  These haven't been
  a focus, an appear to have locking problems causing various deadlocks and
  test failures.

Signed-off-by: David Brown <david.brown@linaro.org>

submanifests/optional.yaml

@@ -60,7 +60,7 @@ manifest:
       groups:
         - optional
     - name: zephyr-lang-rust
-      revision: 49c6712fe53b5b82e5c09e94548a4a51a021acfe
+      revision: 37dc7fac3fb0372bc0e78e022bef87fcce68c48d
       path: modules/lang/rust
       remote: upstream
       groups: