drm/i915/trace: split out display trace to a separate file

Add display/intel_display_trace.[ch] for defining display
tracepoints. The main goal is to reduce cross-includes between gem and
display. It would be possible split up tracing even further, but that
would lead to more boilerplate.

We end up having to include intel_crtc.h in a few places because it was
pulled in implicitly via intel_de.h -> i915_trace.h -> intel_crtc.h, and
that's no longer the case.

There should be no changes to tracepoints.

v3:
- Rebase

v2:
- Define TRACE_INCLUDE_PATH relative to define_trace.h (Chris)
- Remove useless comments (Ville)

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/7862ad764fbd0748d903c76bc632d3d277874e5b.1638961423.git.jani.nikula@intel.com