Change suffix of .f free-form source files to .F90/.f90
For transitioning to cap_gen.py, we must be using the correct filename extension for free-form and fixed-form variables.
I think that currently there are a number of .f files that are free-form and that have hard-coded compiler flags to make this switch. I understand from PR https://github.com/NCAR/ccpp-framework/pull/355 that this is not supported.
In any case, cleaning this up is a good thing.
@climbfuji Not sure if this is still valid? As a reference, I didn't run into any issue with capgen and the file extensions when running the SCM with the GFS v16 suite.
We should look at the .f files in the repo and see if they are manually promoted to free-form because of harcoded compiler switches (which you probably were using with the SCM).