sandbox: mark sandbox_exit() as no return.

Fix a -Wimplicit-fallthrough warning in sandbox_sysreset_request().

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/cpu.c

@@ -31,7 +31,7 @@ static struct udevice *map_dev;
 unsigned long map_len;
 #endif
 
-void sandbox_exit(void)
+void __noreturn sandbox_exit(void)
 {
 	/* Do this here while it still has an effect */
 	os_fd_restore();

arch/sandbox/include/asm/u-boot-sandbox.h

@@ -87,6 +87,6 @@ void sandbox_set_enable_pci_map(int enable);
 void sandbox_reset(void);
 
 /* Exit sandbox (quit U-Boot) */
-void sandbox_exit(void);
+void __noreturn sandbox_exit(void);
 
 #endif	/* _U_BOOT_SANDBOX_H_ */

drivers/sysreset/sysreset_sandbox.c

@@ -65,7 +65,6 @@ static int sandbox_sysreset_request(struct udevice *dev, enum sysreset_t type)
 		if (!state->sysreset_allowed[type])
 			return -EACCES;
 		sandbox_exit();
-		break;
 	case SYSRESET_POWER:
 		if (!state->sysreset_allowed[type])
 			return -EACCES;