RDMA/hns: Fix endian problems around imm_data and rkey

This matches the changes made recently to the userspace hns
driver when it was made sparse clean.

See rdma-core commit bffd380cfe56 ("libhns: Make the provider sparse
clean")

wc->imm_data is not used in the kernel so this change has no practical
impact.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>