Linux 6.6 compat: fsync_bdev() has been removed in favor of sync_blockdev()

In Linux commit 560e20e4bf6484a0c12f9f3c7a1aa55056948e1e, the
fsync_bdev() function was removed in favor of sync_blockdev() to do
(roughly) the same thing, given the same input. This change
conditionally attempts to call sync_blockdev() if fsync_bdev() isn't
discovered during configure.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #15263
(cherry picked from commit 3f67e012e4)

module/os/linux/zfs/zvol_os.c

@@ -694,7 +694,13 @@ zvol_ioctl(struct block_device *bdev, fmode_t mode,
 
 	switch (cmd) {
 	case BLKFLSBUF:
+#ifdef HAVE_FSYNC_BDEV
 		fsync_bdev(bdev);
+#elif defined(HAVE_SYNC_BLOCKDEV)
+		sync_blockdev(bdev);
+#else
+#error "Neither fsync_bdev() nor sync_blockdev() found"
+#endif
 		invalidate_bdev(bdev);
 		rw_enter(&zv->zv_suspend_lock, RW_READER);