udf: Avoid unneeded variable length array in struct fileIdentDesc

impUse variable length array in struct fileIdentDesc is never used.
It serves only for documentation purposes of the on-disk format. Remove
it from the struct so that it doesn't confuse the compiler and
reviewers.

Reported-by: "Gustavo A. R. Silva" <[e-mail]>
References: https://lore.kernel.org/all/ZRrsYkKIQe8K6F/t@work
Signed-off-by: Jan Kara <[e-mail]>

fs/udf/ecma_167.h

···
 	uint8_t		lengthFileIdent;
 	struct long_ad	icb;
 	__le16		lengthOfImpUse;
-	uint8_t		impUse[];
+	/* uint8_t	impUse[]; */
 	/* uint8_t	fileIdent[]; */
 	/* uint8_t	padding[]; */
 } __packed;