ppc: qemu: Create a virtual memory mapping of the platform bus

QEMU ppce500 target can dynamically instantiate an eTSEC device on
a platform bus if "-device eTSEC" is given to QEMU. It is presented
as a "simple-bus" in the device tree, with an additional compatible
string "qemu,platform".

Let's create a virtual memory mapping for it in misc_init_r(), in
preparation to adding eTSEC support.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/board/emulation/qemu-ppce500/Kconfig b/board/emulation/qemu-ppce500/Kconfig
index 4312d98..1c5aa18 100644
--- a/board/emulation/qemu-ppce500/Kconfig
+++ b/board/emulation/qemu-ppce500/Kconfig
@@ -9,4 +9,10 @@
 config SYS_CONFIG_NAME
 	default "qemu-ppce500"
 
+config PLATFORM_BUS_MAP_ADDR
+	hex
+	default 0xf0000000
+	help
+	  The QEMU platform bus base mapped address in the virtual memory space.
+
 endif