hw/arm: Add palmetto-bmc machine

hw/arm: Add palmetto-bmc machine

The new machine is a thin layer over the AST2400 ARM926-based SoC[1].
Between the minimal machine and the current SoC implementation there is
enough functionality to boot an aspeed_defconfig Linux kernel to
userspace. Nothing yet is specific to the Palmetto's BMC (other than
using an AST2400 SoC), but creating specific machine types is preferable
to a generic machine that doesn't match any particular hardware.

[1] http://www.aspeedtech.com/products.php?fPath=20&rId=376

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Message-id: 1458096317-25223-5-git-send-email-andrew@aj.id.au
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>