Revert "sparc64: fix crash in ABI code for { f64, f32 } struct"

This reverts commit 41c6fa8.

compiler/rustc_target/src/abi/call/sparc64.rs

@@ -35,14 +35,12 @@ where
         data.last_offset = data.last_offset + Reg::i32().size;
     }
 
-    if data.last_offset < offset {
-        for _ in 0..((offset - data.last_offset).bits() / 64)
-            .min((data.prefix.len() - data.prefix_index) as u64)
-        {
-            data.prefix[data.prefix_index] = Some(Reg::i64());
-            data.prefix_index += 1;
-            data.last_offset = data.last_offset + Reg::i64().size;
-        }
+    for _ in 0..((offset - data.last_offset).bits() / 64)
+        .min((data.prefix.len() - data.prefix_index) as u64)
+    {
+        data.prefix[data.prefix_index] = Some(Reg::i64());
+        data.prefix_index += 1;
+        data.last_offset = data.last_offset + Reg::i64().size;
     }
 
     if data.last_offset < offset {