[SCSI] isci: fix breakage caused by >16byte CDB patch

Oops, apparently no-one I cc'd at intel actually bothered to check this
patch for the isci driver:

commit e73823f7


Author: James Bottomley <JBottomley@Parallels.com>
Date:   Tue May 7 15:38:18 2013 -0700

    [SCSI] libsas: implement > 16 byte CDB support

sci_swab32_cpy needs multiples of four, so for commands that aren't that, it's
rounding the wrong way.  fix by doing (len+3)/4 instead of len/4.

Reported-by: Tony Luck <tony.luck@intel.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>