target-arm: Wire up AArch64 EL2 and EL3 address translation ops

Wire up the AArch64 EL2 and EL3 address translation operations
(AT S12E1*, AT S12E0*, AT S1E2*, AT S1E3*), and correct some
errors in the ats_write64() function in previously unused code
that would have done the wrong kind of lookup for accesses from
EL3 when SCR.NS==0.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1437751263-21913-3-git-send-email-peter.maydell@linaro.org