hqd: Fix Klocwork errors in liblight

1. Fix null pointer de-reference klocwork error in liblight.
2. sprintf is part of ScanBan function. Replace sprintf with
   snprintf.

Change-Id: I0b88967a2bdf4adf563753c09df88d2c6a432045

liblight/lights.c

@@ -83,7 +83,7 @@ write_int(char const* path, int value)
     fd = open(path, O_RDWR);
     if (fd >= 0) {
         char buffer[20];
-        int bytes = sprintf(buffer, "%d\n", value);
+        int bytes = snprintf(buffer, sizeof(buffer), "%d\n", value);
         ssize_t amt = write(fd, buffer, (size_t)bytes);
         close(fd);
         return amt == -1 ? -errno : 0;
@@ -271,6 +271,10 @@ static int open_lights(const struct hw_module_t* module, char const* name,
     pthread_once(&g_init, init_globals);
 
     struct light_device_t *dev = malloc(sizeof(struct light_device_t));
+
+    if(!dev)
+        return -ENOMEM;
+
     memset(dev, 0, sizeof(*dev));
 
     dev->common.tag = HARDWARE_DEVICE_TAG;