[functorch] Added rot90 batch rule (pytorch/functorch#138)
* Added rot90 batch rule
Description:
- Added rot90 batch rule
- Enabled associated tests
Note: tests seem not be reliable to output bdim.
Tests are passing even if batching rule outputs wrong bdim
* Replaced manual batching rule with REDUCTION_BOXED_ARGS
* Removed commented xfail('rot90')
