drm/i915/selftests: Drop igt_cs_tlb

The gt_tlb live selftest has the same code coverage as the
igt_cs_tlb subtest of gtt, except it is better at detecting
TLB bugs.  Furthermore, while igt_cs_tlb is hitting some
unforeseen issues, these issues are either false positives
due to the test being poorly formatted, or are true
positives that can be more easily diagnosed with smaller
tests.  As such, igt_cs_tlb is superceded by and obsoleted
by gt_tlb, meaning it can be removed.

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230320192117.287374-1-andi.shyti@linux.intel.com