### What this PR does / why we need it?
1. Extracting duplicated code into a method.
That is defining _get_input_parallel_ in parent class
_CustomRowParallelOp_, and call the helper method in its 5 children
classes :
- MLPRowParallelOp
- OProjRowParallelOp
- Flashcomm2OProjRowParallelOp
- MatmulAllreduceRowParallelOp
- SequenceRowParallelOp
's _apply_impl_ method
2. Variable typo fixing: split instead of splitted for the past tense
### Does this PR introduce _any_ user-facing change?
### How was this patch tested?
- vLLM version: v0.16.0
- vLLM main:
4034c3d32e
Signed-off-by: idouba <zhangchaomeng@huawei.com>