riscv: qemu: support booting Linux

Support booting Linux (as payload of BBL) from FIT images. For this, the
default CONFIG_SYS_BOOTM_LEN is increased to 16 MB, and the environment
variables fdt_high and initrd_high are set to mark the device tree and
initrd as in-place.
Signed-off-by: NLukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

configs/qemu-riscv32_defconfig

 CONFIG_RISCV=y
 CONFIG_TARGET_QEMU_VIRT=y
 CONFIG_NR_DRAM_BANKS=1
+CONFIG_FIT=y
 CONFIG_DISPLAY_CPUINFO=y
 CONFIG_DISPLAY_BOARDINFO=y
 CONFIG_OF_PRIOR_STAGE=y

configs/qemu-riscv64_defconfig

@@ -2,6 +2,7 @@ CONFIG_RISCV=y
 CONFIG_TARGET_QEMU_VIRT=y
 CONFIG_ARCH_RV64I=y
 CONFIG_NR_DRAM_BANKS=1
+CONFIG_FIT=y
 CONFIG_DISPLAY_CPUINFO=y
 CONFIG_DISPLAY_BOARDINFO=y
 CONFIG_OF_PRIOR_STAGE=y

include/configs/qemu-riscv.h

@@ -15,7 +15,13 @@
 
 #define CONFIG_SYS_MALLOC_LEN		SZ_8M
 
+#define CONFIG_SYS_BOOTM_LEN		SZ_16M
+
 /* Environment options */
 #define CONFIG_ENV_SIZE			SZ_4K
 
+#define CONFIG_EXTRA_ENV_SETTINGS \
+	"fdt_high=0xffffffffffffffff\0" \
+	"initrd_high=0xffffffffffffffff\0"
+
 #endif /* __CONFIG_H */