RDMA/nes: Modify thermo mitigation to flip SerDes1 ref clk to internal

Change thermo mitigation code to flip the SerDes1 reference clock to
internal, to match the change in commit a4849fc1 ("RDMA/nes: Add
wide_ppm_offset parm for switch compatibility").

Signed-off-by: Chien Tung <chien.tin.tung@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>