Remove whole-array settings to spval for fields that already define l2g_scale_type

Connected with #1297 - Eventually my hope is that we can completely do away with the whole-array settings to spval that we do for any variable written to history file. But that can't happen until we have added the l2g_scale_type / landunit_mask attribute to all history fields that need it.

Something we can do sooner, though is: We should remove the whole-array settings to spval for any history fields that define l2g_scale_type.

We should then confirm that these history fields are bit-for-bit. This will help confirm that their landunit_mask attribute is set correctly.