rust: alloc: fix typo in docs for GFP_NOWAIT

Fix a typo in alloc.rs by replacing Ror with For.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Link: https://lore.kernel.org/r/20240529083452.779865-1-aliceryhl@google.com


Signed-off-by: Miguel Ojeda <ojeda@kernel.org>