guest: sync disk before shutting down

sync() should be called before reboot(RB_AUTOBOOT), otherwise data written
to disks might be lost.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

guest/init.c

@@ -72,6 +72,7 @@ int main(int argc, char *argv[])
 		} while (corpse != child);
 	}
 
+	sync();
 	reboot(RB_AUTOBOOT);
 
 	printf("Init failed: %s\n", strerror(errno));