scsi: qla2xxx: Fix inconsistent DMA mem alloc/free

GPNFT command allocates 2 buffer for switch query. On completion, the same
buffers were freed using different size, instead of using original size at
the time of allocation.

This patch saves the size of the request and response buffers and uses that
to free them.

Following stack trace can be seen when using debug kernel

dump_stack+0x19/0x1b
__warn+0xd8/0x100
warn_slowpath_fmt+0x5f/0x80
check_unmap+0xfb/0xa20
debug_dma_free_coherent+0x110/0x160
qla24xx_sp_unmap+0x131/0x1e0 [qla2xxx]
qla24xx_async_gnnft_done+0xb6/0x550 [qla2xxx]
qla2x00_do_work+0x1ec/0x9f0 [qla2xxx]

Cc: <stable@vger.kernel.org> # v4.17+
Fixes: 33b28357

 ("scsi: qla2xxx: Fix Async GPN_FT for FCP and FC-NVMe scan")
Reported-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>