blockdev: remove bd_block_size_semaphore again

This reverts the block-device direct access code to the previous
unlocked code, now that fs/buffer.c no longer needs external locking.

With this, fs/block_dev.c is back to the original version, apart from a
whitespace cleanup that I didn't want to revert.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/raw.c b/drivers/char/raw.c
index 0bb207e..54a3a6d 100644
--- a/drivers/char/raw.c
+++ b/drivers/char/raw.c
@@ -285,7 +285,7 @@
 
 static const struct file_operations raw_fops = {
 	.read		= do_sync_read,
-	.aio_read	= blkdev_aio_read,
+	.aio_read	= generic_file_aio_read,
 	.write		= do_sync_write,
 	.aio_write	= blkdev_aio_write,
 	.fsync		= blkdev_fsync,