Consistent use of types MeshT and SolverT in recent GPU kernels

[benegee]

Missed in #2590

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 63.63636% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.09%. Comparing base (aca6995) to head (597f138).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/solvers/dgsem_p4est/dg_2d.jl	57.14%	3 Missing ⚠️
src/solvers/dgsem_structured/dg_2d.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2901   +/-   ##
=======================================
  Coverage   97.09%   97.09%           
=======================================
  Files         609      609           
  Lines       47493    47493           
=======================================
  Hits        46111    46111           
  Misses       1382     1382           

Flag	Coverage Δ
unittests	97.09% <63.64%> (ø)

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[ranocha]

Thanks!