fi_ep_bind: call fi_bind with correct field

Manpage says that fi_ep_bind has the following signature:

int fi_ep_bind(struct fid *ep, struct fid *fid, uint64_t flags);

and fi_bind has the following signature:

int fi_bind(struct fid *fid, struct fid *bfid, uint64_t flags);

The macro fi_ep_bind was passing the incorrect type to fi_bind
resulting in compiler warnings.

Signed-off-by: Sayantan Sur <sayantan.sur@intel.com>