[iscsi] Fix iBFT when no explicit initiator name setting exists

Commit 7cfdd76 ("[block] Describe all SAN devices via ACPI tables")
changed the definition of the iSCSI initiator IQN in the iBFT to
represent a common initiator IQN used for all iSCSI sessions, and
attempted to calculate this common initiator IQN by fetching the
common ${initiator-iqn} setting.

This fails when no explicit ${initiator-iqn} has been specified
(i.e. when an initiator IQN has instead been constructed from either
the hostname or system UUID), and results in an empty initiator IQN in
the iBFT.

Fix by using the initiator IQN of an arbitrary iSCSI session
present in the iBFT.

Debugged-by: Tal Aloni <tal.aloni.il@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/block/ibft.c

  *
  * @v initiator		Initiator portion of iBFT
  * @v strings		iBFT string block descriptor
+ * @v initiator_iqn	Initiator IQN
  * @ret rc		Return status code
  */
 static int ibft_fill_initiator ( struct ibft_initiator *initiator,
-				 struct ibft_strings *strings ) {
+				 struct ibft_strings *strings,
+				 const char *initiator_iqn ) {
 	int rc;
 
 	/* Fill in common header */
 				    IBFT_FL_INITIATOR_FIRMWARE_BOOT_SELECTED );
 
 	/* Fill in initiator name */
-	if ( ( rc = ibft_set_string_setting ( NULL, strings,
-					      &initiator->initiator_name,
-					      &initiator_iqn_setting ) ) != 0 )
+	if ( ( rc = ibft_set_string ( strings, &initiator->initiator_name,
+				      initiator_iqn ) ) != 0 )
 		return rc;
 	DBG ( "iBFT initiator name = %s\n",
 	      ibft_string ( strings, &initiator->initiator_name ) );
 	/* Fill in Initiator block */
 	initiator = ( data + initiator_offset );
 	table->control.initiator = cpu_to_le16 ( initiator_offset );
-	if ( ( rc = ibft_fill_initiator ( initiator, &strings ) ) != 0 )
+	iscsi = list_first_entry ( &ibft_model.descs, struct iscsi_session,
+				   desc.list );
+	if ( ( rc = ibft_fill_initiator ( initiator, &strings,
+					  iscsi->initiator_iqn ) ) != 0 )
 		goto err_initiator;
 
 	/* Fill in NIC blocks */