xhci: add traces for debug messages in xhci_address_device()

This patch declares an event class for trace events that
trace messages with variadic arguments, called xhci_log_msg,
and defines a trace event for tracing the debug messages in
xhci_address_device() function, called xhci_dbg_address.

In order to implement this type of trace events, a wrapper function,
called xhci_dbg_trace(), was created that records the format string
and variadic arguments into a va_format structure which is passed as
argument to the tracepoints of the class xhci_log_msg.

All the xhci_dbg() calls in xhci_address_device() are replaced
with calls to xhci_dbg_trace(). The functionality of xhci_dbg()
log messages was not removed though, but it is placed inside
xhci_dbg_trace().

This trace event aims to give the ability to the user or the
developper to isolate and trace the debug messages generated
when an Address Device Command is issued to xHC.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/Makefile

@@ -4,6 +4,9 @@
 
 ccflags-$(CONFIG_USB_DEBUG) := -DDEBUG
 
+# tell define_trace.h where to find the xhci trace header
+CFLAGS_xhci-trace.o := -I$(src)
+
 isp1760-y := isp1760-hcd.o isp1760-if.o
 
 fhci-y := fhci-hcd.o fhci-hub.o fhci-q.o
@@ -13,6 +16,7 @@ fhci-$(CONFIG_FHCI_DEBUG) += fhci-dbg.o
 
 xhci-hcd-y := xhci.o xhci-mem.o
 xhci-hcd-y += xhci-ring.o xhci-hub.o xhci-dbg.o
+xhci-hcd-y += xhci-trace.o
 xhci-hcd-$(CONFIG_PCI)	+= xhci-pci.o
 
 ifneq ($(CONFIG_USB_XHCI_PLATFORM), )