usb/bulk-streams.txt: convert to ReST and add to driver-api book

This document describe some USB core functions. Add it to the
driver-api book.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/driver-api/usb/index.rst

···
    usb
    gadget
    anchors
+   bulk-streams
    writing_usb_driver
    writing_musb_glue_layer
 

Documentation/usb/bulk-streams.txt Documentation/driver-api/usb/bulk-streams.rst

···
+USB bulk streams
+~~~~~~~~~~~~~~~~
+
 Background
 ==========
 
···
 Driver implications
 ===================
 
-int usb_alloc_streams(struct usb_interface *interface,
+::
+
+  int usb_alloc_streams(struct usb_interface *interface,
 		struct usb_host_endpoint **eps, unsigned int num_eps,
 		unsigned int num_streams, gfp_t mem_flags);
 
···
 
 
 Picking new Stream IDs to use
-============================
+=============================
 
 Stream ID 0 is reserved, and should not be used to communicate with devices.  If
 usb_alloc_streams() returns with a value of N, you may use streams 1 though N.
···
 ========
 
 If a driver wishes to stop using streams to communicate with the device, it
-should call
+should call::
 
-void usb_free_streams(struct usb_interface *interface,
+  void usb_free_streams(struct usb_interface *interface,
 		struct usb_host_endpoint **eps, unsigned int num_eps,
 		gfp_t mem_flags);