Fix clippy errors

kernel/src/arch/x86_64/memmap.rs

@@ -48,9 +48,8 @@ pub static _KERNEL_PHYSICAL_MEMORY_OFFSET: Lazy<(u64, u64)> = Lazy::new(|| {
 ///
 /// Panics if the memory map was not found in MEMORY_MAP_REQUEST.
 pub fn get_memory_map() -> &'static MemoryMapResponse {
-    if let Some(memory_map) = MEMORY_MAP_REQUEST.get_response() {
-        memory_map
-    } else {
-        unreachable!("Could not fetch memory map from Limine.")
-    }
+    MEMORY_MAP_REQUEST.get_response().map_or_else(
+        || unreachable!("Could not fetch memory map from Limine."),
+        |memory_map| memory_map,
+    )
 }