scsi: lpfc: Remove lock contention target write path

Lower IOps performance with write operations. Perf tool shows lock
contention in dma_pool_alloc and dma_pool_free related to the
txrdy_payload_pool.

The allocations are for dma buffers for XFER_RDY's, which actually are not
needed for the FCP_TRECEIVE command as the command contents are used by the
adapter to generate the IU.

Remove the allocations and the associated buffer pool.  Rather than leaving
NULLs in buffer pointer locations, set command and sgl to indicate skipped
SGLE indexes.

Link: https://lore.kernel.org/r/20191018211832.7917-10-jsmart2021@gmail.com
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>