riscv: qemu: detect and boot the kernel passed by QEMU

QEMU embeds the location of the kernel image in the device tree. Store
this address in the environment as variable kernel_start. It is used in
the board-local distro boot command QEMU to boot the kernel with the
U-Boot device tree. The QEMU boot command is added as the first boot
target device.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
diff --git a/board/emulation/qemu-riscv/Kconfig b/board/emulation/qemu-riscv/Kconfig
index 37a80db..be5839b 100644
--- a/board/emulation/qemu-riscv/Kconfig
+++ b/board/emulation/qemu-riscv/Kconfig
@@ -29,5 +29,6 @@
 	imply CMD_EXT2
 	imply CMD_EXT4
 	imply CMD_FAT
+	imply BOARD_LATE_INIT
 
 endif