RDMA: Fix comment typo

The double `get' is duplicated, remove one.

Link: https://lore.kernel.org/r/20220722021833.15669-1-gaoxin@cdjrlc.com


Signed-off-by: Xin Gao <gaoxin@cdjrlc.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>