arm: Add Aspeed machine

Aspeed devices are a common Baseboard Management Controller (BMC)
system on chip containing an ARM9 or ARM11 core, off-chip DDR RAM and
support for a large number of peripherals.

This patch adds basic support for the ast2400 and ast2500 machines,
capable of booting to a prompt in QEMU (-M palmetto-bmc), on an
Palmetto OpenPower development machine, and on the ast2500 EVB.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index cdfa6c2..c4512f6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -775,6 +775,8 @@
 
 source "arch/arm/mach-moxart/Kconfig"
 
+source "arch/arm/mach-aspeed/Kconfig"
+
 source "arch/arm/mach-mv78xx0/Kconfig"
 
 source "arch/arm/mach-imx/Kconfig"