rust: iommu: fix Rust formatting

The Rust kernel code should be kept `rustfmt`-clean [1].

Thus run the `rustfmt` target to fix the formatting issue.

Link: https://rust-for-linux.com/contributing#submit-checklist-addendum [1]
Fixes: 2e2f6b0 ("rust: iommu: add io_pgtable abstraction")
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

Author: ojeda

rust/kernel/iommu/pgtable.rs

@@ -14,7 +14,7 @@ use crate::{
     bindings,
     device::{
         Bound,
-        Device //
+        Device, //
     },
     devres::Devres,
     error::to_result,