drm/i915/gt: Convert the final GEM_TRACE to GT_TRACE and co

Convert the few remaining GEM_TRACE() used for debugging over to the
appropriate GT_TRACE or RQ_TRACE.

References: 639f2f24 ("drm/i915: Introduce new macros for tracing")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200106114234.2529613-4-chris@chris-wilson.co.uk