riscv: enable CONFIG_CMD_SBI for QEMU boards

Let CONFIG_TARGET_QEMU_VIRT imply CONFIG_CMD_SBI.

The sbi command provides detailed information about the SBI.
It is useful to test the discovery of extensions.
Signed-off-by: NHeinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

board/emulation/qemu-riscv/Kconfig

@@ -37,6 +37,7 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	imply SPL_RAM_DEVICE
 	imply CMD_PCI
 	imply CMD_POWEROFF
+	imply CMD_SBI
 	imply CMD_SCSI
 	imply CMD_PING
 	imply CMD_EXT2