RDMA/core: Make rdma_counter.h compile stand alone

5.4-rc1 will have new compile time debugging to test that headers can be
compiled stand alone. Many rdma headers are already broken and excluded
from the mechanism, however to avoid compile failures during the merge
window fix enough so that the newly added header compiles clean.

Fixes: 413d3347 ("RDMA/counter: Add set/clear per-port auto mode support")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Mark Zhang <markz@mellanox.com>