riscv: qemu: Add syscon reboot and poweroff support

This adds syscon reboot and poweroff support to QEMU RISC-V.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>
diff --git a/board/emulation/qemu-riscv/Kconfig b/board/emulation/qemu-riscv/Kconfig
index ad99b08..617c4aa 100644
--- a/board/emulation/qemu-riscv/Kconfig
+++ b/board/emulation/qemu-riscv/Kconfig
@@ -53,5 +53,9 @@
 	imply NVME
 	imply SPL_RAM_SUPPORT
 	imply SPL_RAM_DEVICE
+	imply SYSRESET
+	imply SYSRESET_SYSCON
+	imply CMD_POWEROFF
+	imply SYSRESET_CMD_POWEROFF
 
 endif