scsi: esas2r: Switch to flexible array member

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), avoid intentionally writing across
neighboring array fields.

Remove old-style 1-byte array in favor of a flexible array[1] to avoid
future false-positive cross-field memcpy() warning in:

esas2r_vda.c:
	memcpy(vi->cmd.gsv.version_info, esas2r_vdaioctl_versions, ...)

The change in struct size doesn't change other structure sizes (it is
already maxed out to 256 bytes, for example here:

        union {
                struct atto_ioctl_vda_scsi_cmd scsi;
                struct atto_ioctl_vda_flash_cmd flash;
                struct atto_ioctl_vda_diag_cmd diag;
                struct atto_ioctl_vda_cli_cmd cli;
                struct atto_ioctl_vda_smp_cmd smp;
                struct atto_ioctl_vda_cfg_cmd cfg;
                struct atto_ioctl_vda_mgt_cmd mgt;
                struct atto_ioctl_vda_gsv_cmd gsv;
                u8 cmd_info[256];
        } cmd;

No sizes are calculated using the enclosing structure, so no other
updates are needed.

Link: https://lore.kernel.org/r/20210528181337.792268-3-keescook@chromium.orgReviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/esas2r/atioctl.h

@@ -1141,7 +1141,7 @@ struct __packed atto_ioctl_vda_gsv_cmd {
 
 	u8 rsp_len;
 	u8 reserved[7];
-	u8 version_info[1];
+	u8 version_info[];
 	#define ATTO_VDA_VER_UNSUPPORTED 0xFF
 
 };