riscv: qemu: use device tree passed by prior boot stage

QEMU provides a device tree, which is passed to U-Boot using register
a1. We are now able to directly select the device tree with the
configuration CONFIG_OF_PRIOR_STAGE. Replace the hard-coded address in
qemu-riscv with it.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>

board/emulation/qemu-riscv/qemu-riscv.c

@@ -9,8 +9,6 @@
 #include <virtio_types.h>
 #include <virtio.h>
 
-#define MROM_FDT_ADDR	0x1020
-
 int board_init(void)
 {
 	/*
@@ -21,12 +19,3 @@ int board_init(void)
 
 	return 0;
 }
-
-void *board_fdt_blob_setup(void)
-{
-	/*
-	 * QEMU loads a generated DTB for us immediately
-	 * after the reset vectors in the MROM
-	 */
-	return (void *)MROM_FDT_ADDR;
-}

configs/qemu-riscv32_defconfig

@@ -3,4 +3,4 @@ CONFIG_TARGET_QEMU_VIRT=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_DISPLAY_CPUINFO=y
 CONFIG_DISPLAY_BOARDINFO=y
-CONFIG_OF_BOARD=y
+CONFIG_OF_PRIOR_STAGE=y

configs/qemu-riscv64_defconfig

@@ -4,4 +4,4 @@ CONFIG_ARCH_RV64I=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_DISPLAY_CPUINFO=y
 CONFIG_DISPLAY_BOARDINFO=y
-CONFIG_OF_BOARD=y
+CONFIG_OF_PRIOR_STAGE=y