sandbox: implement runtime system reset

Implement a reset function that we can call after ExitBootServices(),
when all driver model devices are gone.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 8746e10..073d90c 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -233,7 +233,8 @@
 	# bool "Reset runtime service is available"
 	bool
 	default y
-	depends on ARCH_BCM283X || FSL_LAYERSCAPE || PSCI_RESET || SYSRESET_X86
+	depends on ARCH_BCM283X || FSL_LAYERSCAPE || PSCI_RESET || \
+		   SANDBOX || SYSRESET_X86
 
 config EFI_GRUB_ARM32_WORKAROUND
 	bool "Workaround for GRUB on 32bit ARM"