scsi: qla2xxx: Sanitize payload size to prevent member overflow

In qla27xx_copy_fpin_pkt() and qla27xx_copy_multiple_pkt(), the frame_size
reported by firmware is used to calculate the copy length into
item->iocb. However, the iocb member is defined as a fixed-size 64-byte
array within struct purex_item.

If the reported frame_size exceeds 64 bytes, subsequent memcpy calls will
overflow the iocb member boundary. While extra memory might be allocated,
this cross-member write is unsafe and triggers warnings under
CONFIG_FORTIFY_SOURCE.

Fix this by capping total_bytes to the size of the iocb member (64 bytes)
before allocation and copying. This ensures all copies remain within the
bounds of the destination structure member.

Fixes: 875386b98857 ("scsi: qla2xxx: Add Unsolicited LS Request and Response Support for NVMe")
Signed-off-by: Jiasheng Jiang <[e-mail]>
Reviewed-by: Himanshu Madhani <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/qla2xxx/qla_isr.c

···
 		payload_size = sizeof(purex->els_frame_payload);
 	}
 
+	if (total_bytes > sizeof(item->iocb.iocb))
+		total_bytes = sizeof(item->iocb.iocb);
+
 	pending_bytes = total_bytes;
 	no_bytes = (pending_bytes > payload_size) ? payload_size :
 		   pending_bytes;
···
 
 	total_bytes = (le16_to_cpu(purex->frame_size) & 0x0FFF)
 	    - PURX_ELS_HEADER_SIZE;
+
+	if (total_bytes > sizeof(item->iocb.iocb))
+		total_bytes = sizeof(item->iocb.iocb);
+
 	pending_bytes = total_bytes;
 	entry_count = entry_count_remaining = purex->entry_count;
 	no_bytes = (pending_bytes > sizeof(purex->els_frame_payload))  ?