drm/xe/compat: remove unused i915_gpu_error.h

The last user of the compat header was removed in commit d6b93391
("drm/i915/dmc: convert intel_dmc_print_error_state() to drm_printer").

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240930164052.3862911-1-jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>