configs/qemu: update arm vexpress

Switch to kernel 4.0.
Switch to DTB (mandatory).
And adjust invocation to use dtb and add a little more RAM for testing.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

board/qemu/arm-vexpress/readme.txt

@@ -1,8 +1,8 @@
 Run the emulation with:
 
-  qemu-system-arm -M vexpress-a9 -kernel output/images/zImage -drive file=output/images/rootfs.ext2,if=sd -append "console=ttyAMA0,115200 root=/dev/mmcblk0" -serial stdio -net nic,model=lan9118 -net user
+  qemu-system-arm -M vexpress-a9 -m 256 -kernel output/images/zImage -dtb output/images/vexpress-v2p-ca9.dtb -drive file=output/images/rootfs.ext2,if=sd -append "console=ttyAMA0,115200 root=/dev/mmcblk0" -serial stdio -net nic,model=lan9118 -net user
 
 The login prompt will appear in the terminal that started Qemu. The
 graphical window is the framebuffer.
 
-Tested with QEMU 2.2.0
+Tested with QEMU 2.2.1

configs/qemu_arm_vexpress_defconfig

@@ -13,14 +13,16 @@ BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
 BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set
 
-# Lock to 3.18 headers to avoid breaking with newer kernels
+# Lock to 4.0 headers to avoid breaking with newer kernels
 BR2_KERNEL_HEADERS_VERSION=y
-BR2_DEFAULT_KERNEL_VERSION="3.18.8"
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_3_18=y
+BR2_DEFAULT_KERNEL_VERSION="4.0"
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_0=y
 
 # Kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="3.18.8"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.0"
 BR2_LINUX_KERNEL_DEFCONFIG="vexpress"
 BR2_LINUX_KERNEL_ZIMAGE=y
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="vexpress-v2p-ca9"