Minor corrections for mixed mode support in AM5

[uramirez8707]

Description
This PR includes some fixes needed for mixed mode support in AM5:

1. Return the correct version of the lon and lat in atmosphere_boundary
2. Fix a typo so that the correct constants in fv_grid_tools.F90 are included
3. Added missing parenthesis when setting z_bot in get_bottom_mass, this was causing answer changes when using the non-mixed precision version of am5

Fixes # (issue)

How Has This Been Tested?
Ran AM5 with and without mixed precision

Checklist:
Please check all whether they apply or not

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[bensonr]

lgtm