sg: relax 16 byte cdb restriction

 - remove the 16 byte CDB (SCSI command) length limit from the sg driver
   by handling longer CDBs the same way as the bsg driver. Remove comment
   from sg.h public interface about the cmd_len field being limited to 16
   bytes.
 - remove some dead code caused by this change
 - cleanup comment block at the top of sg.h, fix urls

Change-Id: I4152a4ebb8c17140bf47e61a8b5b906e9ec4d945
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Git-commit: 65c26a0f39695ba01d9693754f27ca76cc8a3ab5
Git-repo: https://android.googlesource.com/kernel/msm


Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>