RDMA/uverbs: Declare local function static and add brackets to sizeof

Commit 57520751 ("IB/SA: Add OPA path record type") introduced
new local function __ib_copy_path_rec_to_user, but didn't limit its
scope. This produces the following sparse warning:

	drivers/infiniband/core/uverbs_marshall.c:99:6: warning:
	symbol '__ib_copy_path_rec_to_user' was not declared. Should it be
	static?

In addition, it used sizeof ... notations instead of sizeof(...), which
is correct in C, but a little bit misleading. Let's change it too.

Fixes: 57520751

 ("IB/SA: Add OPA path record type")
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>