usb/uas: add usb_pipe_usage_descriptor

usb_pipe_usage_descriptor defines the struct which is used to describe
the type of the endpoint in UAS (status/command/data in+out). It will be
used by the UAS gadget, the host code is using a char array for the
access.

Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Signed-off-by: Sarah Sharp <[e-mail]>

include/linux/usb/uas.h

···
 	__u8 sense[SCSI_SENSE_BUFFERSIZE];
 };
 
+struct usb_pipe_usage_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+
+	__u8  bPipeID;
+	__u8  Reserved;
+} __attribute__((__packed__));
+
 enum {
 	CMD_PIPE_ID		= 1,
 	STATUS_PIPE_ID		= 2,