Temporarily disable a false-positive clippy lint

Clippy says this code can be rewritten with a `?`, but the suggested
change is not valid.

Tracked in #303 to revert
this change once clippy is fixed.

Author: nicholasbishop

src/alloc.rs

@@ -60,6 +60,8 @@ unsafe impl GlobalAlloc for Allocator {
         let align = layout.align();
 
         if align > 8 {
+            // TODO: https://github.com/rust-osdev/uefi-rs/issues/303
+            #[allow(clippy::question_mark)]
             // allocate more space for alignment
             let ptr = if let Ok(ptr) = boot_services()
                 .as_ref()