scsi: core: don't preallocate small SGL in case of NO_SG_CHAIN
The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't
support SG_CHAIN, preallocation of small SGL can't work at all.
Fix this issue by not using small preallocation in case of NO_SG_CHAIN.
Cc: Christoph Hellwig <hch@lst.de> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Ewan D. Milne <emilne@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Guenter Roeck <linux@roeck-us.net> Reported-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>