RDMA: Correct duplicated words in comments

There is a duplicated word 'is' and 'for' in a comment that needs to be
dropped.

Link: https://lore.kernel.org/r/20220622170853.3644-1-jiangjian@cdjrlc.com
Link: https://lore.kernel.org/r/20220623103708.43104-1-jiangjian@cdjrlc.com


Signed-off-by: Jiang Jian <jiangjian@cdjrlc.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>