bsd-user: Add target.h for aarch64.

For aarch64, it's a 64-bit API, so there's no pairing of registers for
64-bit values.

Signed-off-by: Warner Losh <imp@bsdimp.com>

bsd-user/aarch64/target.h

@@ -0,0 +1,20 @@
+/*
+ * Aarch64 general target stuff that's common to all aarch details
+ *
+ * Copyright (c) 2022 M. Warner Losh <imp@bsdimp.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef TARGET_H
+#define TARGET_H
+
+/*
+ * aaarch64 ABI does not 'lump' the registers for 64-bit args.
+ */
+static inline bool regpairs_aligned(void *cpu_env)
+{
+    return false;
+}
+
+#endif /* TARGET_H */