powerpc/pseries: use memdup_user_nul

Use memdup_user_nul() helper instead of open-coding to simplify the code.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pseries/reconfig.c

@@ -367,16 +367,9 @@ static ssize_t ofdt_write(struct file *file, const char __user *buf, size_t coun
 	char *kbuf;
 	char *tmp;
 
-	if (!(kbuf = kmalloc(count + 1, GFP_KERNEL))) {
-		rv = -ENOMEM;
-		goto out;
-	}
-	if (copy_from_user(kbuf, buf, count)) {
-		rv = -EFAULT;
-		goto out;
-	}
-
-	kbuf[count] = '\0';
+	kbuf = memdup_user_nul(buf, count);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
 
 	tmp = strchr(kbuf, ' ');
 	if (!tmp) {