If possible, set more lnd -> mediator coupling fields to spval over ocean

In #1495 (ctsm5.1.dev061), @mvertens set a bunch of lnd -> mediator coupling fields to spval over ocean. But she was not able to do this for every field. I'm not sure of the details, but I think she got unexpected answer changes when trying to set some fields to spval over ocean.

We should come back to this at some point and see if we can set more (maybe all) fields to spval over ocean, and if not, determine why not. (Could this indicate an issue somewhere in the mapping or merging, for example?)