scsi: megaraid_sas: struct MR_HOST_DEVICE_LIST: Replace 1-element array with flexible array

Replace the deprecated[1] use of a 1-element array in struct
MR_HOST_DEVICE_LIST with a modern flexible array.

One binary difference appears in megasas_host_device_list_query():

        struct MR_HOST_DEVICE_LIST *ci;
	...
        ci = instance->host_device_list_buf;
	...
        memset(ci, 0, sizeof(*ci));

The memset() clears only the non-flexible array fields. Looking at the rest
of the function, this appears to be fine: firmware is using this region to
communicate with the kernel, so it likely never made sense to clear the
first MR_HOST_DEVICE_LIST_ENTRY.

Link: KSPP#79 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20240711155841.work.839-kees@kernel.org
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: kees

drivers/scsi/megaraid/megaraid_sas.h

@@ -814,12 +814,12 @@ struct MR_HOST_DEVICE_LIST {
 	__le32			size;
 	__le32			count;
 	__le32			reserved[2];
-	struct MR_HOST_DEVICE_LIST_ENTRY	host_device_list[1];
+	struct MR_HOST_DEVICE_LIST_ENTRY	host_device_list[] __counted_by_le(count);
 } __packed;
 
 #define HOST_DEVICE_LIST_SZ (sizeof(struct MR_HOST_DEVICE_LIST) +	       \
 			      (sizeof(struct MR_HOST_DEVICE_LIST_ENTRY) *      \
-			      (MEGASAS_MAX_PD + MAX_LOGICAL_DRIVES_EXT - 1)))
+			      (MEGASAS_MAX_PD + MAX_LOGICAL_DRIVES_EXT)))
 
 
 /*