scsi: Make sure cmd_flags are 64-bit

cmd_flags in struct request is now 64 bits wide but the scsi_execute
functions truncated arguments passed to int leading to errors. Make sure
the flags parameters are u64.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Jens Axboe <axboe@fb.com>
CC: Jan Kara <jack@suse.cz>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>