Fix broken RRTMGP GPU test in CAM (ESCOMP#316)

Originator(s): sjsprecious

Description (include issue title and the keyword ['closes', 'fixes',
'resolves'] and issue number):

This pull request fixes the broken GPU test of RRTMGP in CAM
(ESCOMP/CAM#1408).

List all namelist files that were added or changed: N/A

List all files eliminated and why: N/A

List all files added and what they do: N/A

List all existing files that have been modified, and describe the
changes:
(Helpful git command: `git diff --name-status
development...<your_branch_name>`)
```
M       schemes/rrtmgp/rrtmgp_sw_gas_optics_pre.F90
```
List all automated tests that failed, as well as an explanation for why
they weren't fixed: N/A

Is this an answer-changing PR? If so, is it a new physics package,
algorithm change, tuning change, etc? No

If yes to the above question, describe how this code was validated with
the new/modified features:

---------

Co-authored-by: cacraigucar <cacraig@ucar.edu>
Co-authored-by: Courtney Peverley <courtneyp@ucar.edu>

Author: 3 people

schemes/rrtmgp/rrtmgp_sw_gas_optics_pre.F90

@@ -39,7 +39,6 @@ subroutine rrtmgp_sw_gas_optics_pre_run(rad_const_array, pmid, pint, nlay, nday,
     ! Local variables
     integer :: i, gas_idx
     integer :: istat
-    real(kind_phys), allocatable :: gas_mmr(:,:)
     real(kind_phys), allocatable :: gas_vmr(:,:)
     real(kind_phys)              :: mmr(nday, nlay)
     real(kind_phys) :: massratio
@@ -59,11 +58,6 @@ subroutine rrtmgp_sw_gas_optics_pre_run(rad_const_array, pmid, pint, nlay, nday,
        return
     end if
 
-    allocate(gas_mmr(nday, pverp-1), stat=errflg, errmsg=alloc_errmsg)
-    if (errflg /= 0) then
-       write(errmsg,*) sub//": failed to allocate 'gas_mmr' - message: "//alloc_errmsg
-       return
-    end if
     allocate(gas_vmr(nday, nlay), stat=errflg, errmsg=alloc_errmsg)
     if (errflg /= 0) then
        write(errmsg,*) sub//": failed to allocate 'gas_vmr' - message: "//alloc_errmsg
@@ -73,11 +67,8 @@ subroutine rrtmgp_sw_gas_optics_pre_run(rad_const_array, pmid, pint, nlay, nday,
 
     do gas_idx = 1, nradgas
 
-       ! grab mass mixing ratio of gas
-       gas_mmr = rad_const_array(:,:,gas_idx)
-
        do i = 1, nday
-          mmr(i,ktoprad:) = gas_mmr(idxday(i),ktopcam:)
+          mmr(i,ktoprad:) = rad_const_array(idxday(i),ktopcam:,gas_idx)
        end do
 
        ! If an extra layer is being used, copy mmr from the top layer of CAM to the extra layer.