target-arm: Add AArch64 translation stub

target-arm: Add AArch64 translation stub

We should translate AArch64 mode separately from AArch32 mode. In AArch64 mode,
registers look vastly different, instruction encoding is completely different,
basically the system turns into a different machine.

So let's do a simple if() in translate.c to decide whether we can handle the
current code in the legacy AArch32 code or in the new AArch64 code.

So far, the translation always complains about unallocated instructions. There
is no emulator functionality in this patch!

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: John Rigby <john.rigby@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1378235544-22290-11-git-send-email-peter.maydell@linaro.org
Message-id: 1368505980-17151-5-git-send-email-john.rigby@linaro.org
[PMM:
 * provide no-op versions of a64 functions ifndef TARGET_AARCH64;
   this lets us avoid #ifdefs in translate.c
 * insert the missing call to disas_a64_insn()
 * stash the insn in the DisasContext rather than reloading it in
   real_unallocated_encoding()
]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>