Modify EndpointInfo to provide meaningful data rather than raw USB

descriptor values. E.g. for the user, the distinction between
MaxIsoPkt and MaxPktSize is irrelevant, only the calculated max packet
size matters.

usb/endpoint_info_test.go

@@ -14,12 +14,14 @@
 
 package usb
 
+import "time"
+
 // IN bulk endpoint
 var testBulkInEP = EndpointInfo{
-	Address:       0x82,
-	Attributes:    uint8(TransferTypeBulk),
+	Number:        2,
+	Direction:     EndpointDirectionIn,
 	MaxPacketSize: 512,
-	PollInterval:  1,
+	TransferType:  TransferTypeBulk,
 }
 
 var testBulkInSetup = InterfaceSetup{
@@ -31,11 +33,11 @@ var testBulkInSetup = InterfaceSetup{
 
 // OUT iso endpoint
 var testIsoOutEP = EndpointInfo{
-	Address:       0x06,
-	Attributes:    uint8(TransferTypeIsochronous),
-	MaxPacketSize: 3<<11 + 1024,
-	MaxIsoPacket:  3 * 1024,
-	PollInterval:  1,
+	Number:        6,
+	MaxPacketSize: 3 * 1024,
+	TransferType:  TransferTypeIsochronous,
+	PollInterval:  125 * time.Microsecond,
+	UsageType:     IsoUsageTypeData,
 }
 
 var testIsoOutSetup = InterfaceSetup{