usb: xhci-dbg: Display endpoint number and direction in context dump

When CONFIG_XHCI_HCD_DEBUGGING is activated, the XHCI driver can dump
device and input contexts to the console. The endpoint contexts in that
dump are labeled "Endpoint N Context", where N is the XHCI endpoint
index (DCI - 1). This can be very confusing, especially for people who
are not that familiar with the XHCI specification. This patch introduces
an xhci_get_endpoint_address function (as a counterpart to the reverse
xhci_get_endpoint_index), and uses it to additionally display the
endpoint number and direction when dumping contexts, which are much more
commonly used concepts in USB.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>