USB: rename usb_buffer_alloc() and usb_buffer_free() users

For more clearance what the functions actually do,

  usb_buffer_alloc() is renamed to usb_alloc_coherent()
  usb_buffer_free()  is renamed to usb_free_coherent()

They should only be used in code which really needs DMA coherency.

All call sites have been changed accordingly, except for staging
drivers.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Pedro Ribeiro <pedrib@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/DocBook/writing_usb_driver.tmpl b/Documentation/DocBook/writing_usb_driver.tmpl
index eeff19c..bd97a13 100644
--- a/Documentation/DocBook/writing_usb_driver.tmpl
+++ b/Documentation/DocBook/writing_usb_driver.tmpl
@@ -342,7 +342,7 @@
 {
     kfree (dev->bulk_in_buffer);
     if (dev->bulk_out_buffer != NULL)
-        usb_buffer_free (dev->udev, dev->bulk_out_size,
+        usb_free_coherent (dev->udev, dev->bulk_out_size,
             dev->bulk_out_buffer,
             dev->write_urb->transfer_dma);
     usb_free_urb (dev->write_urb);