Fix cudf_assert in cudf::io::orc::gpu::gpuDecodeOrcColumnData

[davidwendt]

This fixes the cudf_assert check in an ORC reader device function that checks an offsets value does not exceed a size_type. The assert expression was just coded backwards and so was being triggered for valid values.

This PR fixes the assert expression.

The assert only occurs in a debug build since it is compiled out of a release build. Also, test code for this code path was only recently added.

[codecov]

Codecov Report

Merging #9348 (fb4ecf3) into branch-21.12 (ab4bfaa) will decrease coverage by 0.03%.
The diff coverage is 1.76%.

@@               Coverage Diff                @@
##           branch-21.12    #9348      +/-   ##
================================================
- Coverage         10.79%   10.75%   -0.04%     
================================================
  Files               116      116              
  Lines             18869    19482     +613     
================================================
+ Hits               2036     2096      +60     
- Misses            16833    17386     +553     

Impacted Files	Coverage Δ
python/cudf/cudf/_lib/__init__.py	0.00% <ø> (ø)
python/cudf/cudf/core/_base_index.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/categorical.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/column.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/datetime.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/lists.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/numerical.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/string.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/timedelta.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/dataframe.py	0.00% <0.00%> (ø)
... and 80 more

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[karthikeyann]

@gpucibot merge