Adds missing tags to nested do loops in math functions

[ngs333]

This PR adds missing tags to nested do loops in math functions in file fms_diag_fieldbuff_update.fh. The tags were present in the baseline for some time before the buffer update (math) function PR was created,
but somehow they were omitted.

Fixes # (issue)

How Has This Been Tested?
Standard unit tests pass. Some tests that reproduced the problem were
ran and they also pass.

Checklist:

• [X ] My code follows the style guidelines of this project
• [ X] I have performed a self-review of my own code
• [X ] I have commented my code, particularly in hard-to-understand areas
• [X ] I have made corresponding changes to the documentation
• [ X] My changes generate no new warnings
• [X ] Any dependent changes have been merged and published in downstream modules
• [ X] New check tests, if applicable, are included
• [X ] make distcheck passes

[uramirez8707]

I did a quick run with SPEAR and the history files are now reproducing. @rem1776 @thomas-robinson i think this should be merged so we could do more, longer tests.

[thomas-robinson]

@rem1776 merge and tag with 2023.01-beta2