RDMA/mlx5: Delete declaration of already removed function

The implementation of mlx5_core_page_fault_resume() was removed in commit
d5d284b8 ("{net,IB}/mlx5: Move Page fault EQ and ODP logic to
RDMA"). This patch removes declaration too.

Fixes: d5d284b8 ("{net,IB}/mlx5: Move Page fault EQ and ODP logic to RDMA")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>