scsi: qla2xxx: Replace one-element array with DECLARE_FLEX_ARRAY() helper

One-element arrays as fake flex arrays are deprecated and we are moving
towards adopting C99 flexible-array members, instead. So, replace
one-element array declaration in struct ct_sns_gpnft_rsp, which is
ultimately being used inside a union:

drivers/scsi/qla2xxx/qla_def.h:
3240 struct ct_sns_gpnft_pkt {
3241         union {
3242                 struct ct_sns_req req;
3243                 struct ct_sns_gpnft_rsp rsp;
3244         } p;
3245 };

Refactor the rest of the code, accordingly.

This issue was found with the help of Coccinelle.

Link: https://github.com/KSPP/linux/issues/245
Link: https://github.com/KSPP/linux/issues/193Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/ZH+/rZ1R1cBjIxjS@workSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_def.h

@@ -3174,12 +3174,12 @@ struct ct_sns_gpnft_rsp {
 		uint8_t vendor_unique;
 	};
 	/* Assume the largest number of targets for the union */
-	struct ct_sns_gpn_ft_data {
+	DECLARE_FLEX_ARRAY(struct ct_sns_gpn_ft_data {
 		u8 control_byte;
 		u8 port_id[3];
 		u32 reserved;
 		u8 port_name[8];
-	} entries[1];
+	}, entries);
 };
 
 /* CT command response */

drivers/scsi/qla2xxx/qla_gs.c

@@ -3776,8 +3776,8 @@ int qla24xx_async_gpnft(scsi_qla_host_t *vha, u8 fc4_type, srb_t *sp)
 		sp->u.iocb_cmd.u.ctarg.req_size = GPN_FT_REQ_SIZE;
 
 		rspsz = sizeof(struct ct_sns_gpnft_rsp) +
-			((vha->hw->max_fibre_devices - 1) *
-			    sizeof(struct ct_sns_gpn_ft_data));
+			vha->hw->max_fibre_devices *
+			    sizeof(struct ct_sns_gpn_ft_data);
 
 		sp->u.iocb_cmd.u.ctarg.rsp = dma_alloc_coherent(&vha->hw->pdev->dev,
 								rspsz,