ROMFS: Advance destination buffer pointer when reading from a blockdev

RomFS should advance the destination buffer pointer when reading data from a
blockdev source (the data may be split over multiple blocks, each requiring its
own sb_read() call).  Without this, all the data is copied to the beginning of
the output buffer.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/romfs/storage.c

@@ -120,6 +120,7 @@ static int romfs_blk_read(struct super_block *sb, unsigned long pos,
 			return -EIO;
 		memcpy(buf, bh->b_data + offset, segment);
 		brelse(bh);
+		buf += segment;
 		buflen -= segment;
 		pos += segment;
 	}