sd: Fix max transfer length for 4k disks

sd: Fix max transfer length for 4k disks

The following patch fixes an issue observed with 4k sector disks
where the max_hw_sectors attribute was getting set too large in
sd_revalidate_disk. Since sdkp->max_xfer_blocks is in units
of SCSI logical blocks and queue_max_hw_sectors is in units of
512 byte blocks, on a 4k sector disk, every time we went through
sd_revalidate_disk, we were taking the current value of
queue_max_hw_sectors and increasing it by a factor of 8. Fix
this by only shifting sdkp->max_xfer_blocks.

Cc: [email protected]
Signed-off-by: Brian King <[email protected]>
Reviewed-by: Paolo Bonzini <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>