[why]
dcn301_calculate_wm_and_dl() causes flickering when external monitor is
connected.

This issue has been fixed before by commit 0e4c0ae5
("drm/amdgpu/display: drop dcn301_calculate_wm_and_dl for now"), however
part of the fix was gone after commit 2cbcb78c ("Merge tag 'amd-drm-next-5.13-2021-03-23' of https://gitlab.freedesktop.org/agd5f/linux into drm-next").

[how]
Use dcn30_calculate_wm_and_dlg() instead as in the original fix.

Fixes: 2cbcb78c ("Merge tag 'amd-drm-next-5.13-2021-03-23' of https://gitlab.freedesktop.org/agd5f/linux into drm-next")
Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Zhan Liu <zhan.liu@amd.com>
Tested-by: Zhan Liu <zhan.liu@amd.com>
Tested-by: Oliver Logush <oliver.logush@amd.com>
Signed-off-by: Zhan Liu <zhan.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>