realcomplex_even: remove dead 2D/3D pre/post processing code
realcomplex_even: remove dead 2D/3D pre/post processing code

Those cases are now handled by realcomplex_even_transpose, which fuses the
pre/post processing with the preceding/following transpose.
ROCmSoftwarePlatform/rocFFT,ROCmSoftwarePlatform/rocFFT,ROCmSoftwarePlatform/rocFFT,ROCmSoftwarePlatform/rocFFT