xhci: Add missing parameter description to xhci_get_endpoint_index()

JIRA: https://issues.redhat.com/browse/RHEL-116016

commit 85c4aa0
Author: Hans Zhang <18255117159@163.com>
Date: Tue, 6 May 2025 11:31:01 +0800

  Fix kernel-doc warning by documenting the @desc parameter:

  drivers/usb/host/xhci.c:1369: warning: Function parameter or struct member 'desc' not described in 'xhci_get_endpoint_index'

  Add detailed description of the @desc parameter and clarify the indexing
  logic for control endpoints vs other types. This brings the documentation
  in line with kernel-doc requirements while maintaining technical accuracy.

  Signed-off-by: Hans Zhang <18255117159@163.com>
  Link: https://lore.kernel.org/r/20250506033101.206180-1-18255117159@163.com
  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Desnes Nunes <desnesn@redhat.com>

Author: Desnes Nunes

drivers/usb/host/xhci.c

@@ -1459,6 +1459,7 @@ static void xhci_unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
  * xhci_get_endpoint_index - Used for passing endpoint bitmasks between the core and
  * HCDs.  Find the index for an endpoint given its descriptor.  Use the return
  * value to right shift 1 for the bitmask.
+ * @desc: USB endpoint descriptor to determine index for
  *
  * Index  = (epnum * 2) + direction - 1,
  * where direction = 0 for OUT, 1 for IN.