hw/intc/arm_gic: reserved register addresses are RAZ/WI
    
    The GICv2 specification says that reserved register addresses
    must RAZ/WI; now that we implement external abort handling
    for Arm CPUs this means we must return MEMTX_OK rather than
    MEMTX_ERROR, to avoid generating a spurious guest data abort.
    
    Cc: qemu-stable@nongnu.org
    Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
    Message-id: 1513183941-24300-3-git-send-email-peter.maydell@linaro.org
    Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
    (cherry picked from commit 0cf09852015e47a5fbb974ff7ac320366afd21ee)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>