tests: codegen-llvm: Update bpf-alu32 with the new LLVM attributes

The LLVM backend now emits `noundef zeroext` on `i8` return values and
`noundef` on `i8` parameters. Update the FileCheck pattern to match.

Author: vadorovsky

tests/codegen-llvm/bpf-alu32.rs

@@ -5,7 +5,7 @@
 
 #[no_mangle]
 #[target_feature(enable = "alu32")]
-// CHECK: define i8 @foo(i8 returned %arg) unnamed_addr #0 {
+// CHECK: define noundef zeroext i8 @foo(i8 noundef returned %arg) unnamed_addr #0 {
 pub unsafe fn foo(arg: u8) -> u8 {
     arg
 }