* [UnitTest] Disable ptx mma tests on unsupported nvcc versions.
- Modified `tvm.contrib.nvcc.get_cuda_version` to return a
`(major,minor,release)` tuple rather than a float.
- Implemented `tvm.testing.requries_nvcc_version` decorator to specify
the minimum `(major,minor,release)` version needed to run a unit
test.
- Applied decorated to unit tests in `test_tir_ptx_mma.py` that fail
on earlier nvcc versions.
* Fix lint errors.
* Updated a few of the cuda version checks.
* More lint fixes.
* Only compare major/minor in find_libdevice, not release version.
Eric Lunderberg
ffd517ad6e