drm/amd/display: Fix __muldf3 undefined for 32 bit compilation

Sometimes when trying to enable some feature, we have to define some
values with educated guesses, but we mark those values as TBD, which
means "To Be Determined". However, the correct way to approach it is by
loading that information from the firmware. Anyway, some of the values
that we were experimenting with caused this issue:

ERROR: modpost: "__muldf3" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!

This commit fixes this issue by removing the division by two since it is
harmless in this case.

Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Fixes: 265280b9 ("drm/amd/display: add CLKMGR changes for DCN32/321")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>