tools/power/x86/intel-speed-select: Remove warning for unused result

Fix warning for:
isst-config.c: In function ‘set_cpu_online_offline’:
isst-config.c:221:3: warning: ignoring return value of ‘write’,
declared with attribute warn_unused_result [-Wunused-result]
   write(fd, "1\n", 2);
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

tools/power/x86/intel-speed-select/isst-config.c

@@ -169,7 +169,7 @@ int get_topo_max_cpus(void)
 static void set_cpu_online_offline(int cpu, int state)
 {
 	char buffer[128];
-	int fd;
+	int fd, ret;
 
 	snprintf(buffer, sizeof(buffer),
 		 "/sys/devices/system/cpu/cpu%d/online", cpu);
@@ -179,9 +179,12 @@ static void set_cpu_online_offline(int cpu, int state)
 		err(-1, "%s open failed", buffer);
 
 	if (state)
-		write(fd, "1\n", 2);
+		ret = write(fd, "1\n", 2);
 	else
-		write(fd, "0\n", 2);
+		ret = write(fd, "0\n", 2);
+
+	if (ret == -1)
+		perror("Online/Offline: Operation failed\n");
 
 	close(fd);
 }