hw/arm/vexpress: Add alias for flash at address 0 on A15 board

hw/arm/vexpress: Add alias for flash at address 0 on A15 board

The A15 Versatile Express board can remap a variety of things at address
0. We don't currently emulate the Serial Configuration Controller which
is how the guest can control this remapping, but we can provide the
initial default mapping of the first flash device into this space.
In particular this allows QEMU to boot flash images such as UEFI which
expect to include an exception vector table.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Grant Likely <grant.likely@linaro.org>
Message-id: 1373374180-19884-1-git-send-email-peter.maydell@linaro.org