ARM: qemu-arm: Add support for AArch64

This adds support for '-machine virt' on AArch64. This is rather simple:
we just add TARGET_QEMU_ARM_xxBIT to select a few different Kconfig
symbols, provide the ARMv8 memory map from the board file and add a new
defconfig based on the 32-bit defconfig.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-qemu/Kconfig b/arch/arm/mach-qemu/Kconfig
index 3500b56..133163a 100644
--- a/arch/arm/mach-qemu/Kconfig
+++ b/arch/arm/mach-qemu/Kconfig
@@ -10,3 +10,14 @@
 	default "qemu-arm"
 
 endif
+
+config TARGET_QEMU_ARM_32BIT
+	bool "Support qemu_arm"
+	depends on ARCH_QEMU
+	select CPU_V7
+	select ARCH_SUPPORT_PSCI
+
+config TARGET_QEMU_ARM_64BIT
+	bool "Support qemu_arm64"
+	depends on ARCH_QEMU
+	select ARM64