riscv: qemu: Add syscon reboot and poweroff support

This adds syscon reboot and poweroff support to QEMU RISC-V.
Signed-off-by: NBin Meng <bin.meng@windriver.com>
Reviewed-by: NPragnesh Patel <pragnesh.patel@sifive.com>

board/emulation/qemu-riscv/Kconfig

@@ -53,5 +53,9 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	imply NVME
 	imply SPL_RAM_SUPPORT
 	imply SPL_RAM_DEVICE
+	imply SYSRESET
+	imply SYSRESET_SYSCON
+	imply CMD_POWEROFF
+	imply SYSRESET_CMD_POWEROFF
 
 endif