RDMA/ocrdma: Avoid a possible crash in ocrdma_rem_port_stats

debugfs_remove should be called before freeing the driver
stats resources to avoid any crash during ocrdma_remove.

Signed-off-by: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Selvin Xavier <selvin.xavier@avagotech.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>