scsi: megaraid_sas: Convert union megasas_sgl to flex-arrays

In the ongoing effort to replace all fake flexible arrays with true
flexible arrays, replace the sge32, sge64, and sge_skinny members of union
megasas_sgl with true flexible arrays. No binary differences are seen after
this change; sizes were already being manually calculated using the member
struct sizes directly.

Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: megaraidlinux.pdl@broadcom.com
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230511220957.never.919-kees@kernel.orgSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas.h

@@ -1722,11 +1722,9 @@ struct megasas_sge_skinny {
 } __packed;
 
 union megasas_sgl {
-
-	struct megasas_sge32 sge32[1];
-	struct megasas_sge64 sge64[1];
-	struct megasas_sge_skinny sge_skinny[1];
-
+	DECLARE_FLEX_ARRAY(struct megasas_sge32, sge32);
+	DECLARE_FLEX_ARRAY(struct megasas_sge64, sge64);
+	DECLARE_FLEX_ARRAY(struct megasas_sge_skinny, sge_skinny);
 } __attribute__ ((packed));
 
 struct megasas_header {