drm/i915/trace: clean up boilerplate organization

Follow the style that seems to be prevalent in kernel for undef and
define of TRACE_SYSTEM, TRACE_INCLUDE_PATH, and TRACE_INCLUDE_FILE.

There should be no changes to tracepoints.

v2: Keep TRACE_INCLUDE_PATH relative to define_trace.h (Chris)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/0d37790ee70fb60be6f6a73d8bde2013510a7ad8.1638961423.git.jani.nikula@intel.com

drivers/gpu/drm/i915/i915_trace.h

 /* SPDX-License-Identifier: GPL-2.0 */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM i915
+
 #if !defined(_I915_TRACE_H_) || defined(TRACE_HEADER_MULTI_READ)
 #define _I915_TRACE_H_
 
@@ -15,10 +19,6 @@
 #include "i915_drv.h"
 #include "i915_irq.h"
 
-#undef TRACE_SYSTEM
-#define TRACE_SYSTEM i915
-#define TRACE_INCLUDE_FILE i915_trace
-
 /* watermark/fifo updates */
 
 TRACE_EVENT(intel_pipe_enable,
@@ -1337,5 +1337,7 @@ DEFINE_EVENT(i915_context, i915_context_free,
 
 /* This part must be outside protection */
 #undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
 #define TRACE_INCLUDE_PATH ../../drivers/gpu/drm/i915
+#define TRACE_INCLUDE_FILE i915_trace
 #include <trace/define_trace.h>