asm: Work around LLVM bug on AArch64

Upstream issue: https://github.com/llvm/llvm-project/issues/58384

LLVM gets confused if we assign a 32-bit value to a 64-bit register, so
pass the 32-bit register name to LLVM in that case.

src/test/ui/asm/aarch64/llvm-58384.rs

@@ -0,0 +1,16 @@
+// only-aarch64
+// run-pass
+// needs-asm-support
+
+// Test that we properly work around this LLVM issue:
+// https://github.com/llvm/llvm-project/issues/58384
+
+use std::arch::asm;
+
+fn main() {
+    let a: i32;
+    unsafe {
+        asm!("", inout("x0") 435 => a);
+    }
+    assert_eq!(a, 435);
+}