ide-cd: Don't warn on bogus block size unless it actually matters.

Frans Pop reported that his CDROM drive reports a blocksize of 2352,
and this causes new warnings due to commit
e8e7b9eb ("ide-cd: fix oops when using
growisofs").

What we're trying to do is make sure that "blocklen >> SECTOR_BITS"
is something the block layer won't choke on.

And for Frans' case "2352 >> SECTOR_BITS" is equal to
"2048 >> SECTOR_BITS", and thats "4".

So warning in this case gives no real benefit.
Reported-by: NFrans Pop <elendil@planet.nl>
Tested-by: NFrans Pop <elendil@planet.nl>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/ide/ide-cd.c

@@ -876,9 +876,12 @@ static int cdrom_read_capacity(ide_drive_t *drive, unsigned long *capacity,
 		return stat;
 
 	/*
-	 * Sanity check the given block size
+	 * Sanity check the given block size, in so far as making
+	 * sure the sectors_per_frame we give to the caller won't
+	 * end up being bogus.
 	 */
 	blocklen = be32_to_cpu(capbuf.blocklen);
+	blocklen = (blocklen >> SECTOR_BITS) << SECTOR_BITS;
 	switch (blocklen) {
 	case 512:
 	case 1024: