lib: drop generic sense data descriptor VALID check

According to SPC-5 (r17), the sense data descriptor format follows:
byte	field
----	-----
0:	DESCRIPTOR TYPE
1:	ADDITIONAL LENGTH
2-n:	Sense data descriptor specific

The VALID bit is a sense data descriptor specific flag, and is not
present in the only sense data descriptor supported by libiscsi -
Sense key specific sense data descriptors.
Drop the generic VALID bit check, in preparation for handling it on
a sense data descriptor specific basis.

Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: David Disseldorp <ddiss@suse.de>

lib/iscsi-command.c

@@ -328,8 +328,6 @@ static void parse_sense_descriptors(struct scsi_sense *sense, const uint8_t *sb,
 	for (p = sb; p < end; p += p[1]) {
 		if (p[1] < 4) /* length */
 			break;
-		if (!(p[2] & 0x80)) /* VALID bit */
-			break;
 		switch (p[0]) {
 		case 2:
 			/* Sense key specific sense data descriptor */