Fix build error on Linux >= 6.12 by guarding no_llseek

Linux 6.12 removed the no_llseek macro. Add a version check so that
.llseek = no_llseek is only used on kernels prior to 6.12.

Thanks to EricccTaiwan for the review and for pointing out that
similar cleanup could also be done in this repository.

Author: weiso131

simrupt.c

@@ -326,7 +326,9 @@ static const struct file_operations simrupt_fops = {
     .owner = THIS_MODULE,
 #endif
     .read = simrupt_read,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 12, 0)
     .llseek = no_llseek,
+#endif
     .open = simrupt_open,
     .release = simrupt_release,
 };