scsi: qla2xxx: Fix regression warnings

scsi: qla2xxx: Fix regression warnings

drivers/scsi/qla2xxx/qla_dbg.c:2542:7: warning: The scope of the variable 'pbuf'
can be reduced. [variableScope]
drivers/scsi/qla2xxx/qla_init.c:3615:6: warning: Variable 'rc' is assigned a
value that is never used. [unreadVariable]
drivers/scsi/qla2xxx/qla_isr.c:81:11-29: WARNING: dma_alloc_coherent use in
rsp_els already zeroes out memory, so memset is not needed
drivers/scsi/qla2xxx/qla_mbx.c:4889:15-33: WARNING: dma_alloc_coherent use in
els_cmd_map already zeroes out memory, so memset is not needed

[mkp: added newline after variable declaration]

Link: https://lore.kernel.org/r/20200403084018.30766-2-njavali@marvell.com
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>