Use pointer null compare instead of integer compare.

Author: BsAtHome

src/hal/drivers/hal_gpio.c

@@ -165,7 +165,7 @@ int build_chips_collection(char *name, hal_gpio_bulk_t **ptr, int *count){
     struct gpiod_line *temp_line;
 
     temp_line = gpiod_line_find(name);
-    if (temp_line <= 0) {
+    if (!temp_line) {
 	    rtapi_print_msg(RTAPI_MSG_ERR, "The GPIO line %s can not be found\n", name);
 	    return -EINVAL;
     }